Word choice

The right word has the exact meaning, the right tone for the passage, and the right idiom (the preposition that goes with it).

How to do it

Read the sentence with each choice and ask what it would literally mean.
Match the tone. A serious history passage does not use slang ("a ton of," "pretty much") or inflated words.
Check common confusions: affect/effect, than/then, imply/infer, fewer/less, principal/principle.
Check idioms: "different from," "capable of," "a debate about," "in contrast to."

Example

Wrong The prize had a large affect on the work of clockmakers.

Right The prize had a large effect on the work of clockmakers.

After "a large," a noun is needed. "Effect" is the noun; "affect" is usually a verb.

Traps

Two choices that mean nearly the same thing can differ in tone or connotation. "Stubborn" and "persistent" are not the same compliment.
Do not pick a word because it sounds impressive. The plainest word that is exactly right wins.

Practice it

Every practice question comes with a full explanation, including why each wrong choice is wrong. Free, with no account.