Answer:
a. v(t) = x'(t)s(t) + x(t)s'(t)
Step-by-step explanation:
Given an object's position on the x-axis is given by x(t)s(t), you want the velocity of the object.
The velocity is the derivative of position. The derivative of a product is found using the relation ...
(uv)' = u'v +uv'
In this case, that means ...
v(t) = (x(t)s(t))'
v(t) = x'(t)s(t) +x(t)s'(t) . . . . . matching choice A