Doubt 2

The correct answer should be b.
Answer a suggests that the students haven't met with opposition.
Answer c suggests that the students can read without opposition.
Only answer b states that the principal's proposal hasn't met with opposition.

Kasia@MasterGMAT wrote: Only answer b states that the principal's proposal hasn't met with opposition.

@Kasia, Of the three, B is the best.

But I feel that B suggests that Principal has not met with the opposition (not her proposal).
But it is her proposal that should meet (or not meet) the opposition.

Let's try to analyze this sentence in more detail:

The principal has sought approval for her plan to grant promotions to only those 7th grade students proficient in reading, and has not met with opposition

There are two parts of the parallel structure:
1. The principal has sought approval for her plan (...)
2. (the principal - since there is no subject in the second clause after "and" we should assume that the subject remains the same) has not met with opposition

Therefore, we know that the principal has not met with opposition concerning her plan.

yes, its B.

Moreover, "opposition" connects well with "approval".