Some questions must be answered with a cross in a box . If you change your mind about an
answer, put a line through the box and then mark your new answer with a cross .
Movement at a joint involves muscle contraction that requires a supply of ATP.
The diagram below shows muscles that cause movement of bones in the leg.
Place a cross in the box next to the description of the muscles in this diagram.
A the extensor muscle is contracted and the flexor muscle is relaxed
B the extensor muscle and the flexor muscle are both contracted
C the extensor muscle is relaxed and the flexor muscle is contracted
D the extensor muscle and the flexor muscle are both relaxed