B is correct. For A to be grammatically correct and the same in meaning, I would say "Because of their heavy weight, the only thing they could have done was stay on the ground forever."

The correct explanation is that "do you know" is present tense and "have you known" is present perfect. Present perfect means the action was begun in the past and is now complete. You can't ask how long something is happening in the present, but

"I regret damaging your book." is perfectly correct. A little stiff, maybe, but grammatically unflawed. One would normally say "I'm sorry I damaged your book." But back to your question: the present perfect tense "have damaged" makes an awkward

This isn't a question of bad or good, but of formal and informal. Both of your sentences are correct. Contractions ("doesn't") are simply informal.

Money can't buy me love. What is a baby sitter or a chartered jet, if not time purchased?

Enkatesu should really stop giving advice. "Loving" and "needing" in your examples are not gerunds, but present participles. "I am loving it" is common, but "He is needing you" is awkward. "He needs you" is better. FYI, "loving" and "needing"

Enkatesu has no business giving advice. The correct answer is #1: "This is getting far to strong." (Though the subsequent sentences appear unrelated.) I'm afraid the reason why #2 is wrong is idiomatic. "Far" amplifies "too." But "very" weakens

Perhaps you were thinking of "funner", which is wrong.

Suzi, I wouldn't look to politicians for examples of good grammar.

You're right to be confused. The grammar book is wrong. You can, for example say "I've been in China for five days, thirteen hours, forty minutes, and twelve seconds." Is that specific enough? To give the book some credit, although specificity