The variable measures effects of the independent variable
a. confounding
b. dependent
c. experimental
d. independent

B. Dependent variable.

Explanation:

A independent variable is the one which has be manipulated in an experiment. This is a variable which has to be changed so as to observe the effect of change on the dependent variable. A dependent variable is the variable which is also called as experimental variable. It is the outcome of the experiment.

here we know that ball will drop down by total distance 3.2 m

so here we know that

now using kinematics

now in the same time it will cover horizontal distance of 0.75 m

so speed of the ball will be