[1] alejandro’s guidance counselor is him plan his schedule for next year. [2] she suggests that he take ap chemistry and ap french to improve his chances of getting into college. [3] neither he nor his parents think he’ll have time to do the work for both courses. [4] each of the teachers teach in a different way.

which sentence has an indefinite-pronoun verb agreement error?
sentence 1
sentence 2
sentence 3
sentence 4

4. Each of the teachers teach in a different way.

When the words "each", "no" or "every" is placed before a noun (whether plural or singular), the verb must be singular. The correct sentence is "Each of the teachers teaches in a different way"

Sentence 1 is correct because Alejandro’s guidance counselor is one person, more specifically the third person singular, thus the verb "is" is correct. Number 2 is also correct: "She suggests that he take" is in the subjunctive mood and very often, verbs that are followed by a verb such as "suggest" should be in the subjunctive mood form ("take" instead of "takes").  

Sentence 3 is correct as well because when a sentence has the words "Neither" and "nor" and the nouns differ in number (plural or singular), the verb must agree with the noun or pronoun closest to it, in this case "his parents", the closest pronoun to the verb, is in plural, therefore the verb must be in plural too.

D. Sentence 4

we know that, volume of a rectangular prism is given by :

✿   {length × width × height}

given : the length of rectangular prism = 5.5

given : the width of rectangular prism = 6

given : the height of rectangular prism = 3

⇒ the volume of given rectangular prism = {5.5 × 6 × 3}

⇒ the volume of given rectangular prism = 99