The fighting ended in 1975, when, after years of negotiations, *guerilla leaders and white officials had agreed* to the new constitution at the British sponsored talks in London.
A. guerilla leaders and white officials had agreed
B. guerilla leaders and white officials agreed.
C. guerilla leaders and white officials reached an agreement
D. guerilla leaders and white officials were made to agree
E. guerilla leaders and white officials had agreed upon
OA is B.
This question tests the knowledge about usage of verb tense incase of two unrelated events.
A. usage of past perfect "had agreed" is incorrect in this case, because "war ended in 1975" and "two parties agreed" these are two independent events. Whenever there are two independent events they should be in simple past.
B. Option B is correct because it uses simple past. Let's keep it.
C. This is an interesting option, it says two parties reached an agreement, in the original sentence it says two parties agreed on something not an agreement. The difference is "agreed" is a verb and "agreement" is a noun. There is a clear deviation in the meaning of the sentence.
D. In this options, it is complicating the sentence by usage of "were made to agree". As per the context of the sentence, two parties agrees mutually they were not forced to do anything. This option conveys that they were made to agree which is incorrect.
E. This option has two errors, usage of past perfect as in option A and idiom error, "agreed upon to the new..." is incorrect. The correct idiom would be "agreed to".