This question is incomplete. I was able to find the complete question online. It is the following:
1. An internet buyer needs to be especially careful when they buy any type of medicine online because many pills are dangerous, counterfeit products.
2. If a student can't figure out which pronoun to use, you won't do well in college.
3. The clothing manufacturer projects a life expectancy of 50 washings of their product.
4. The placebo effect is demonstrated when a person takes an aspirin and their headache improves in seconds, which can't be the drug, because it takes at least 15 minutes to kick in.
5. A car buyer should consider your driving habits before deciding what car to buy.
Answer:
1. . . . when he/she buys any type of medicine online . . .
2. . . . to use, he/she won't do well in college.
3. . . . of its product.
4. . . . and his/her headache improves . . .
5. . . . consider his/her driving habits . . .
Step-by-step explanation:
It is quite common for us to use the wrong pronoun when substituting words that refer to things or people in general. For instance, we commonly refer to a "person" as "they". In colloquial language, that is acceptable, but formal language considers that pronoun usage incorrect. Since the word "person" refers to the third-person singular, the pronouns to be used with it should be "he" and "she" or, if possessive, "his" and "her".
That is the case with the sentences above. "Person", "buyer", "student", and "manufacturer" are all third-person singular words. As for "manufacturer", since it most likely refers to a company or business, the correct pronoun would be "it" or, if possessive, "its".