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+Exercise 20
+
+For this final exercise, you must create a new Sugar activity from scratch. You
+have two options of activities to create:
+ A. An ‘odd one out’ game. It should display four buttons on the screen, each
+    with a conjugation of a verb as its text. The four conjugations should be
+    different, and one should be incorrect. The user must click on the button
+    with the incorrect conjugation. If they do, their score is increased and
+    another set of four conjugations is displayed. If they click on the wrong
+    button, their score is not incremented and the conjugations do not change.
+    The user must click the odd one out to proceed.
+    The user’s score should be displayed in a label in the toolbar (ask if you
+    need help with this, or look at the code in PascalTriangle which does a
+    similar thing by putting a GtkScale in its toolbar).
+ B. Similar to the above game, but using mathematical equalities instead of
+    verb conjugations. The game should present the user with four equalities
+    (e.g. “5 × 6 + 3 = 33”, “(1 + 4) × 2 = 10”, etc.), one of which should be
+    incorrect. The user must pick the incorrect one to proceed.
+
+Once you’ve created the activity, tested it in emulation and tested it on a
+physical XO, you should get someone else to review all of your code and see if
+they can find any problems with it. Code review like this is always helpful, as
+every programmer makes mistakes (no matter how experienced they are) and a
+fresh pair of eyes can spot them. Ideally, your code should be reviewed by
+someone who wrote the other type of activity to you, so they have to rely on
+comments in your code to work out how the code functions. Remember to comment
+your code well!