Seems to work

Päevaküsimus/Models/Answer.cs

@@ -3,11 +3,30 @@ using System.Collections;
 
 namespace Päevaküsimus.Models
 {
-    public class Answer
+    [Serializable()]
+    public class Answer : NotificationBase, ICloneable
     {
-        public string answer { get; set; }
+        private string _answer;
+        public string answer {
+            get { return _answer; }
+            set
+            {
+                _answer = value;
+                NotifyPropertyChanged();
+            }
+        }
         public bool correct { get; set; }
-        public int selectionCount { get; set; }
+        private int _selectionCount;
+
+        public int selectionCount
+        {
+            get { return _selectionCount; }
+            set
+            {
+                _selectionCount = value;
+                NotifyPropertyChanged();
+            }
+        }
 
         public Answer(string answer)
         {
@@ -20,5 +39,12 @@ namespace Päevaküsimus.Models
             this.answer = answer;
             this.correct = correct;
         }
+
+        public object Clone()
+        {
+            var c = new Answer(answer.Clone() as string, correct);
+            c.selectionCount = selectionCount;
+            return c;
+        }
     }
 }

Päevaküsimus/Models/Question.cs

@@ -4,10 +4,20 @@ using System.Collections.ObjectModel;
 
 namespace Päevaküsimus.Models
 {
-    public class Question
+    [Serializable()]
+    public class Question : NotificationBase, ICloneable
     {
-        public string question { get; set; }
+        private string _question;
+        public string question {
+            get { return _question; }
+            set
+            {
+                _question = value;
+                NotifyPropertyChanged();
+            }
+        }
         private ObservableCollection<Answer> _answers;
+        public ObservableCollection<Answer> answers { get { return _answers; } }
 
         public Question(string question)
         {
@@ -15,11 +25,19 @@ namespace Päevaküsimus.Models
             this._answers = new ObservableCollection<Answer>();
         }
 
-        public ObservableCollection<Answer> answers { get { return _answers; } }
-
         public void AddAnswer(Answer answer)
         {
             _answers.Add(answer);
         }
+
+        public object Clone()
+        {
+            var q = new Question(_question.Clone() as string);
+            foreach (var answer in _answers)
+            {
+                q.AddAnswer(answer.Clone() as Answer);
+            }
+            return q;
+        }
     }
 }