Analyze the following statements about bodies under the effect of multiple forces:
a) Bodies can move freely in any direction.
b) Bodies are often constrained to move on a plane or in a specific direction.
c) A link is any object that prevents the free mobility of the body being studied.
d) It is not necessary to identify the intensity with which the body interacts with each of the other forces.

a) only a and b are correct.
b) only b and c are correct.
c) only b, c, and d are correct.
d) all statements are correct.