Write a letter to your friend telling him or her about an excursion your school went and it's benefit

quite an interesting way to teach topic sentences, because the answer to this question is the best definition of a topic sentence that one can present, it is as if answering the questions taught you how to do it, this is some real teaching, it is terribly well-done.

the topic sentence in this paragraph is:

topic sentences writers stay on track and keep a paragraph from becoming an aimless collection of sentences about an idea.

which incidentally tells you what a topic sentence should be.

the legal limit for the drivers who can drive after consuming any amount of alcohol is 21 years.

explanation:

on november 1, 1996, a "zero tolerance law" was put into effect in the new york state.

according to this zero tolerance law, for people under the age of 21 years, it was illegal to purchase and possess alcohol or to drive after consuming any amount of it.

also, the alcohol involvement rate for the drivers under the age of 21 was roughly twice that of elderly drivers.