Which of the following is not true concerning the curl-up test?
a. the curl-up only tests the endurance of the abdominal muscles, not their strength.
b. curl-ups are performed while lying on the floor with knees slightly bent.
c. the fingers are supposed to slide 3.5 inches along the floor during a curl-up.
d. curl-ups are supposed to be done at a rate of about one every three seconds.