Question 2
Answer: Across the bay, fleets of old fishing boats was seen on the horizon.
Explanation: The subject fleets (plural noun) of old fishing boats mismatches the verb was seen (only for I/he/she/it)
Question 5
Answer: John cried.
Step-by-step explanation: This sentence is the only one with a subject and a predicate. "Because he wasn't hungry" is a reason clause that must depend on another sentence. "Rebekah drove a race car she won three races" is not a valid sentence unless you place a semicolon after the word "car" to separate the two predicates in it (or a period to make two separate sentences).
Question 10
Answer: I studied
Explanation: The subject "I" is not properly divided from the verb (studied), complement (for the test) and the independent clause joined by the word "but" (but I still didn't pass it).