A．Because we can succeed only by making mistakes.
B．Because it is necessary for us to make mistakes if we want to be successful.
C．Because making mistakes means giving us more useful knowledge.
D．Because all the book knowledge is gained by making mistakes.

A．To attract more sea animals to the testing site.
B．To drive dangerous sea animals away from the testing site.
C．To help track the sea animals being tested.
D．To determine how sea animals communicate with each other.