1. b. is correct.
2. a. is incorrect. Subject is "editing" - a gerund, which is considered singular.
3. b. is incorrect. Subject is "Vitamins" - a plural noun, and it needs a plural verb. The clause "that are sold in a health-food store" is getting in your way and confusing you.
how come 1 can't be a
1a.Did you know a famous animal-rights activist has criticized horseracing because of the dangers involved?
1b. Did you know a famous animal-rights activist have criticized horseracing because of the dangers involved?
Subject-verb agreemnet? I choose b.
In this sentence, the main subject is "you," but the subject you're being asked about is in a subordinate clause. That subject is "activist" -- singular or plural??
so you use have when it is singular right that's why I choose b.
The form "have" is not to be used with 3rd person singular subjects; the form "has" needs to be used in that case.
You can say these:
But you must use "has" with all 3rd person singular subjects, such as he, she, it, "activist," or any other SINGULAR noun or pronoun.
Scroll down to section 4 which identifies person (1st, 2nd, and 3rd) and number (singular and plural).
Sorry, I see the confusion now. My error in my first response for you.
1.a. is correct.
some athletes have taken drug tests to prove they are not on steroids.
vitamins that are sold in a heath-food store are not regulated by the Food and Drug Administration
vitamins that are sold in a health-food store are not regulated bye th food and drug Administration
which one of these sentences are a subject verb agreement