-

diff --git a/DuolingoMobile/Sources/Explanations/ExplanationCells.swift b/DuolingoMobile/Sources/Explanations/ExplanationCells.swift
index b29ff18c1..aa34831f2 100644
--- a/DuolingoMobile/Sources/Explanations/ExplanationCells.swift
+++ b/DuolingoMobile/Sources/Explanations/ExplanationCells.swift
@@ -209,7 +209,7 @@ class OptionsCell: ExplanationCell {
             let missingButtons = max(0, model.count - buttons.count)
             if missingButtons > 0 {
                 let newButtons = (0..<missingButtons).map { _ in
-                    OptionsCell.makeButton()
+                    OptionsCell.makeButton(target: self)
                 }
                 for button in newButtons {
                     buttons.append(button)
@@ -233,36 +233,38 @@ class OptionsCell: ExplanationCell {
         }
     }
 
-    var optionTapped: ((Int) -> Void)?
+    var optionTapped: ((OptionsCell, Int) -> Void)?
 
     typealias RadioButton = DUOCheckBoxButton
 
-    private var buttons: [RadioButton] = {
-        (0..<2).map { _ in
-            OptionsCell.makeButton()
-        }
-    }()
+    private var buttons: [RadioButton] = []
 
-    private static func makeButton() -> RadioButton {
+    private static func makeButton(target: OptionsCell?) -> RadioButton {
         let style = DUOStyle.default()
         let radioButton = DUOCheckBoxButton(frame: .zero, style: style)!
         radioButton.isRadioButton = true
         radioButton.font = style.lightFont
         radioButton.textAlignment = .left
         radioButton.layOutRightToLeft = false
+        if let target = target {
+            radioButton.addTarget(target, action: #selector(OptionsCell.handleOptionTap(_:)), for: .touchUpInside)
+        }
         return radioButton
     }
 
     @objc override init(frame: CGRect) {
         super.init(frame: frame)
 
+        buttons = (0..<2).map { _ in
+            OptionsCell.makeButton(target: self)
+        }
         for button in buttons {
             contentView.addSubview(button)
         }
 
-        // XXX don't need this
-        let tapRecognizer = UITapGestureRecognizer(target: self, action: #selector(OptionsCell.handleTap(_:)))
-        contentView.addGestureRecognizer(tapRecognizer)
+//        // XXX don't need this
+//        let tapRecognizer = UITapGestureRecognizer(target: self, action: #selector(OptionsCell.handleTap(_:)))
+//        contentView.addGestureRecognizer(tapRecognizer)
     }
 
     override func layoutSubviews() {
@@ -330,7 +332,7 @@ class OptionsCell: ExplanationCell {
 
     static func height(forModel model: Model, maxWidth: CGFloat) -> CGFloat {
         let buttons: [RadioButton] = model.map {
-            let button = self.makeButton()
+            let button = self.makeButton(target: nil)
             button.text = $0.text
             return button
         }
@@ -339,12 +341,16 @@ class OptionsCell: ExplanationCell {
     }
 
     @objc
-    func handleTap(_ sender: UITapGestureRecognizer) {
+    func handleOptionTap(_ sender: RadioButton) {
         guard let currentModel = currentModel else {
             return
         }
 
-        optionTapped?(0)
+        guard let buttonIndex = buttons.index(of: sender) else {
+            assertionFailure("Button that was tapped doesn't exist?")
+            return
+        }
+        optionTapped?(self, buttonIndex)
     }
 
     required init?(coder aDecoder: NSCoder) {
diff --git a/DuolingoMobile/Sources/Explanations/ExplanationsVC.swift b/DuolingoMobile/Sources/Explanations/ExplanationsVC.swift
index 91cc8520f..87ffc348b 100644
--- a/DuolingoMobile/Sources/Explanations/ExplanationsVC.swift
+++ b/DuolingoMobile/Sources/Explanations/ExplanationsVC.swift
@@ -387,14 +387,16 @@ class ExplanationsVC: UIViewController, UICollectionViewDataSource, UICollection
 
     private var images: [URL: PDFImage] = [:]
 
-    private func flattenedElement(atIndex index: Int) -> Either<(Element, isPartOfChallenge: Bool), [Option]> {
+    typealias ChallengeID = String
+
+    private func flattenedElement(atIndex index: Int) -> Either<(Element, isPartOfChallenge: Bool), (identifier: ChallengeID, options: [Option])> {
         // XXX maybe don't compute this all the time.
         var flattenedElements: [Either<(ExplanationsElement, isPartOfChallenge: Bool), [Option]>] = []
         for element in currentElements {
             switch element {
             case .challenge(let model):
                 flattenedElements += model.elements.map({ .left(($0, isPartOfChallenge: true)) })
-                flattenedElements += [.right(model.options)]
+                flattenedElements += [.right((model.identifier, model.options))]
             default:
                 flattenedElements += [.left((element, isPartOfChallenge: false))]
             }
@@ -483,7 +485,7 @@ class ExplanationsVC: UIViewController, UICollectionViewDataSource, UICollection
             let cell = collectionView.dequeueReusableCell(withReuseIdentifier: OptionsCell.reuseIdentifier(),
                                                           for: indexPath) as! OptionsCell
             cell.currentModel = options
-            cell.optionTapped = { [weak self] optionIndex in
+            cell.optionTapped = { [weak self] (cell, optionIndex) in
                 guard
                     let strongSelf = self,
                     let oldExplanation = strongSelf.currentExplanation
@@ -495,6 +497,11 @@ class ExplanationsVC: UIViewController, UICollectionViewDataSource, UICollection
                 // Tell the server that this challenge was answered.
                 // XXX ?
 
+                // Determine the challenge that was answered.
+                let indexPath = strongSelf.collectionView.indexPath(for: cell)
+                let challengeModel: ChallengeElementModel
+                let element = currentElements[indexPath?.row]
+
                 // Mark the challenge as answered.
                 let newChallengeModel = challengeModel.answered
                 let newElement = ExplanationsElement.challenge(newChallengeModel)