Click on the clip, then fill in the gaps with the past form of the following verbs:
to blow, to be, to hear, to go, to come, to know, to think
Then press "Check" to check your answers. Use the "Hint" button to get a free letter if an answer is giving you trouble. You can also click on the "[?]" button to get a clue. Note that you will lose points if you ask for hints or clues!