5a. Some athletes have taken drug tests to prove they are not on steroids.

5b. Some athletes have took drug tests to prove they are not on steroids.

Using regular and irregular verbs

6a. I lay my book on the table, but now I cannot find it.

6b. I laid my book on the table, but now I cannot find it.

Using the correct form of be and have in the present tense

7a. I was interested in working on the presidential campaign if the opportunity still exists.

7b. I am interested in working on the presidential campaign if the opportunity still exists.

Verb form and verb tense

8a. Since American Idol premiered on television, many talented contestants have appeared on the show.

8b. Since American Idol premiered on television, many talented contestants appeared on the show.

I know 5 is a 6 is b 7 is b and 8 is b