The OA is D

dimonya wrote:Ya b is correct.

the rationale in my opinion is as follows:

1. here agreement established the precedent.

2. although it was done in the past, the precedent was established at the time of the agreement.

3 thus we have agreement (cause) precedent (effect) at the same time <=> present continuous tense is appropriate (establishing)

B

I agree the B is correct.

here, "establising" can not logically happen before "contributing" as "truce" happen logically before "helping to keep" in Q 51, OG 11

so d is correct in Q51

this is a bad sentence which immitate OG but do so wrongly.

that is why Stacey refuse to comment

Hello friends. I wish we discuss good questions, even only questions from OG. we think we fully understand the questions in OG but in fact we dose not. I thing fully understanding OG is enough to get 700. Many question I post from OG, but no one answers. the explanation in OG is very short even I can say, nearly it dose not explain.

do not discuss this question any more. we do not have time. this kind of question destroy our study. OG from ETS which is mother of GMAT.