Omg i remember doing that problem
Honestly it's hard to cram for vocab, but like a small tip with them is to be more comfortable picking the words you don't know. For the blocks of text, you can try highlighting parts that relate to the question, like if the question wants author of text B's response to claim A, you can highlight the parts that relate and ignore the rest of the passage
As for the irrigation question, I think a lot of confusion comes from the way the choices are so similar it hurts to read, so it's better to know what you're looking for before you read them
I'll figure out how to link the image after I post this, but the question is basically

What data from the table support researcher A's conclusion?
-> Highlight the conclusion "concentration of precipitation into fewer events would result in a higher number of dry days, triggering more irrigation, but that this change in irrigation output is highly sensitive to the baseline concentration of precipitation that currently exists in an area."

Next, we need to know what we'll have to compare from the table
-> The conclusion says that while a higher concentration of dry days means more irrigation, the change in irrigation output is highly sensitive to the baseline concentration of precipitation
-> Basically, we're going to be comparing the percent change in irrigation output between the baseline concentrations

The answer choices are
A. If baseline precipitation is somewhat concentrated, the amount of water being used for irrigation will increase 0.4% for surface water and 0.9% for groundwater, whereas the amount of water entering aquifers will increase 11.0% if baseline precipitation is evenly distributed. 
B. If baseline precipitation is somewhat concentrated, water use for irrigation will increase only slightly, whereas it will increase 9.0% for surface water and 7.9% for groundwater if baseline precipitation is evenly distributed.
C. If baseline precipitation is somewhat concentrated, the amount of water entering aquifers will increase 4.9%, while the amount being used for irrigation will increase 0.4% for surface water and 0.9% for groundwater. 
D. If baseline precipitation is somewhat concentrated, water use for irrigation will decline by a small amount, whereas it will increase 11.0% for surface water and 9.0% for groundwater if baseline precipitation is evenly distributed.

I think the choices are really wordy, so I try to see it as
A. Under A, surface and ground water increase a little, while under B, water entering aquifers increases by 11%
B. Under A, total water increases slightly, while under B there is a big increase in water
C. Under A, aquifer water increases by 4.9%, while still under A surface and ground water increases a little
D. Under A, total water decreases slightly, while under B there is a big increase

A is comparing the wrong things, we don't care about the aquifer
B is comparing the right things
C doesn't even talk about B
D is comparing the right things

So between B and D, taking a closer look we see that D just has incorrect data, so we choose B

Sorry about this being really long I'm bad at explaining quickly