Why is the answer C?

Explanation:
The horizontal velocity reached by the mass is:
v = v₀ + at
vₓ = 0 + (F/m) (1 s − 0 s)
vₓ = F/m
The force is then removed, so the mass continues at this horizontal velocity.
The vertical velocity reached by the mass is:
v = v₀ + at
vᵧ = 0 + (F/m) (2 s − 1 s)
vᵧ = F/m
The force is then removed, so the mass continues at this vertical velocity.
So at 2 seconds, the mass's velocity has equal components in the x and y directions, and continues to have that velocity at 3 seconds.