Economic analysts predict that there is going to be considerable alter

Hi aaba,

Another great question! First, let's fix a minor typo in your original question - the phrase at the end "in the coming months" shouldn't be underlined. This might help you find the correct answer faster!

Economic analysts predict that there is going to be considerable alterations to the interest rate in the coming months.

Okay, with this small change, we can go through each answer and check for problems. The first problem I noticed is in the original sentence - subject/verb agreement. So let's go through each answer and look for subject/verb agreement problems. Hopefully this will narrow things down!

(A) there is going to be considerable alterations to the interest rate
This is WRONG because the singular "is" doesn't match what it's referring to - the plural "alterations."

(B) the interest rate are going to alter considerably
This is WRONG because the plural verb "are" doesn't match the singular subject "rate."

(C) there are going to be considerable alterations to the interest rate
This is OK because "are" and "alterations" are both plural, so let's keep this for later.

(D) considerable alterations to the interest rate will occur
This is also OK because there are not subject/verb disagreements.

(E) the interest rate will change considerably
This is also OK because the subject and verb agree.

So based on subject/verb agreement, we can eliminate answers A & B. Now that we have it narrowed down, let's look at each answer plugged into the rest of the sentence, and look for any issues we can find:

(C) Economic analysts predict that there are going to be considerable alterations to the interest rate in the coming months.

This is INCORRECT because it uses passive voice, which is highly discouraged in the GMAT SC portion. It's also not clear that the interest rate will actually change (aka raise or lower) - just that it'll be "altered" in some way.

(D) Economic analysts predict that considerable alterations to the interest rate will occur in the coming months.

This is also INCORRECT because it uses passive voice. It's also unclear if the rate itself will go up or down - it'll just be "altered" in some way.

(E) Economic analysts predict that the interest rate will change considerably in the coming months.

This is CORRECT because it has proper subject/verb agreement, is written in active voice, and is clear that the interest rate will change.