Answer
The correct answer is: (a)
Work Step by Step
Let the initial velocity be $v_{0y}$. We can find an expression for the vertical velocity as a function of time:
$v_y = v_{0y}-9.80~t$
We can find an expression for the momentum $p_y$ as a function of time:
$p_y = m~v_y = m~( v_{0y}-9.80~t) = (-9.80~m)~t+m~v_{0y}$
This graph is a straight line with a y-intercept of $(m~v_{0y})$ and a slope of $-(9.80~m)$
The correct answer is: (a)
