If you know that a person is running 100 feet every 12 seconds, you can determine their
a. acceleration
b. force
c. mass
d. velocity

None of the choices is a correct answer.

a). acceleration
No.  There may be acceleration, if the person is running
in a circle or on a curve.  But you can't tell from only the
information you have.

b). force
No.  You can't tell what forces may be acting on the person
just from the information you have.

c). mass
No.  People of all different masses can run 100 feet every
12 seconds. You can't determine the person's mass just from
the information you have.

d). velocity
Close, but NO.
From the information you have, you can determine the person's speed.

Speed is  (distance covered) / (time to cover the distance)

             =                (100 feet) / (12 seconds)

             =                          (100/12)  feet/second

             =                              8-1/3 feet per second .

That's speed.  Not velocity.

In order to tell the person's velocity, you also need to know
what direction the person is running, and you don't have that
information.  So you can't determine his velocity either.

None of the choices is a correct answer.

Ibelieve your answer is b.hope this : )