Please answer correctly

I think that C) and D)

Step-by-step explanation:

I think this because if you look at 3.5 secounds it came down and after 1.75 secounds the ball hit the ground. A) wouldn't be because it came down at 3.5 secounds not coming up. B) wouldn't be because the ball droped after 1.75 secounds not come up.

answer: the dogs need to shift their focus to human scent.

its because the dogs being trained are for search and rescue thus they need to be able to track humans and their specific scent