Answer:
5N
Explanation:
We have a simple problem of momentum here. 
ΔMomentum= mΔv= FΔt
Solve for F
mΔv/Δt=F
Plug in givens
1*(2-1.5)/0.1=F
F=5N
 
        
             
        
        
        
C.
Thanks me later, that's my answer.
        
             
        
        
        
Velocity = displacement (distance)/time
v=80m/4s
v=20m/s
velocity = 20 meters per second
        
             
        
        
        
<span>C. Does eating less fat increase a mouse's lifespan?
(If a mouse eats less fat in its meals then will it live longer: compared to other mice lives.
</span>This is a testable question that can be answered by designing and conducting an experiment.
I think D could be correct as well.
My final answer is D.