The paragraph is missing a period at the end.
Since "Growing flowers is one of my happiest childhood memories." is the topic sentence, then the rest of the paragraph should be supporting THAT statement.
The topic sentence is not necessarily a HOOK, more like a regular statement. A good hook would be something including a sound, a question, or using descriptive words.
Answer:
and where are the sentences
I believe the correct answer is the third one.
