A. The correct answer is 5. verb tenses disagree.
In the first part of the sentence, a past verb (was down) is used. This means that the verb in the latter part of the sentence also has to be in the past form. However, this is not the case - a present verb (see) is used. It should be - when I saw - which is why this sentence is incorrect because the verb tenses don't match.
B. The correct answer is 3. compound subject and verb disagree.
The subject Maria and Thomas is a compound subject. This means that the subject contains more than one word/entity, and as you can see here, this subject has two parts joined by the conjunction AND. A compound subject takes a plural verb - so it should be GO instead of GOES.
C. The correct answer is 4. indefinite pronoun and verb disagree.
The pronoun EACH is an indefinite pronoun, meaning that we don't know exactly who the pronoun is referring to (the same is with someone, anyone, etc.) This pronoun takes a singular verb - which means that the verb should be IS GOING, rather than ARE GOING.
D. The correct answer is 2. collective noun and verb disagree.
The noun THE COMPANY is a collective noun. This can mean two things: it can either take a singular verb (if you are referring to the entire company as one entity), or a plural verb (if you are referring to each of the employees separately). In the case above, the verb is wrong - it should be singular IS instead of plural ARE.
E. The correct answer is 1. subject disagrees with the verb it comes after.
The subject of the sentence is YOUR FAMILY AND BEST FRIEND and it comes after the verb IS. The verb is wrong - it should be plural ARE instead of singular IS because the subject is compound, like in sentence B. Since there are two entities mentioned, they take a plural verb instead of a singular one.
