What is the main idea

The main idea is quite literally the main idea of your essay/paper.

if your essay is about how sea turtles are being affected by plastic straws, that’s your main idea.

your supporting details are the things that are supporting your argument!

Explanation:

d) the narrator even suggested that the white whale, moby d, was ubiquitous and present in every ocean at every moment.  

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.