Question

2. We can develop phobias of virtually anything. Most phobias start in childhood but they can also develop

Answer 1

Answer:

Most phobias start in childhood, but they can also develop  in adults.

Explanation:

In the given sentence, a comma between the noun childhood and conjunction but is necessary.

This is a compound sentence. A compound sentence is a sentence that consists of at least two independent clauses joined by a comma, semicolon, or conjunction. When we use a conjunction to connect two independent clauses, it should be preceded by a comma. That's why the original sentence is incorrect.