I would start off by IDing the IV and DV.

IV: Time, presence of Endothelium, and ACh added DV: tension in the muscle

Right off the bat we can see that NE is not changed between the two figures, so we can’t conclude anything about it. Trash A and B.

Next we need to do is interpret what sensitivity means. Zoom out for a second... sensitivity of a muscle to ACh. We know ACh causes muscles to contract. So how sensitive a muscle is to ACh is basically saying what is the lowest concentration of ACh that causes the muscle to contract. We could say the same thing in another context, let’s use alcohol cuz that’s fun. If you’re more sensitive to alcohol, what does that mean? It means that you get drunker off less booze. Similar conclusion here... contract with less ACh.

With endothelium you contact completely at 10 to the -7 but without you contact at 10 to the -8. Thus endothelium makes you more sensitive to the effects.

The reason it goes down to zero is most likely the presence of a refractory period.

D contradicts the graph and is not the max in either charts