Generate the answer for a given question. The question requires common knowledge of English. Make sure that the answer is in detail, long, consistent with the context, and requires general knowledge of English. To be less repetitive, please vary your language for each question. Give a proper explanation to answer, and if necessary, provide the definition of various terms. And conclude your answer if it's long. If you have used other resources (e.g., Merriam Webster's.) to answer the question, include citations in your answer. You don't need to paraphrase the context of your resources, but make sure that your answer is consistent and complete.

Q: How should you reply to 'what's up?'.

A: 'What's up' means 'What's happening.' I usually just reply 'nothing.' because nothing is happening to me. But, there are alternatives, such as the usual reply to a greeting: Not much Nothing. Yourself? I'm good, yourself? Good. How are you? However, if there is something that you would like to tell the other person e.g. You've sold your car, it might go like this: A: What's up? B: I've sold my car. A: Good on you mate!
****
Q: Is there a specific rule, or set of rules, that can be followed to know when to use each word? I have noticed that not is usually used with a verb, but I think that there sometimes are exceptions although I can't think of one now.

A: Not is a negative adverb; no is a negative quantifier; non- is a negative prefix. Since negation is so important, thousands of idioms use each of these, among other negatives. Consequently there are lots of exceptions to the general rules below. Non- is not a word, but a part of another word, usually a descriptive adjective: non-lethal, non-professional, non-native, non-technical, non-playing (The hyphen is optional.) Each of these mean 'anything but ...' -- anything that doesn't kill you is non-lethal, anything that's not technical is non-technical, etc. This meaning contrasts with un- and in-, which refer to opposites instead of complements. No is half of the answer pair Yes/No, shading off vocally into Nah, Nuh-uh, and Uh-uh. But it can also quantify and negate any noun phrase: Some blade of grass ~ No blade of grass; One who saw it ~ No one who saw it. Not is the general negator for verb phrases, including predicate adjectives and nouns. In a verb phrase, not occurs immediately after the first auxiliary verb. If there is no auxiliary verb in the verb phrase, Do-Support supplies a form of do. Not is contracted whenever possible, with auxiliaries or subjects (especially pronouns): He's not interested ~ He isn't interested; She doesn't like it, but not *She not likes it. Any of these negatives (and many others) can negate a sentence, changing its truth value. It's easy to switch between them, too; the sentences below all mean the same thing: They allowed no phone calls. They didn't allow phone calls. No one allowed phone calls. Phone calls weren't allowed.
****
Q: What is the meaning of wrt in the following text? I think this is an excellent idea, but I'd like to see this explicitly reframed under the banner of providing Drupal.org data through publicly-accessible APIs. We started kicking off at least one discussion like that wrt Git over, which also led back to '#112805: XML-RPC Interface'.

A:
It's an abbreviation for 'with respect to'. Edit: regarding the lack of punctuation (thanks for bringing it up, ukayer), that's definitely because of the informal nature of the context. It would be more standard to write it as w.r.t., except that in any context where punctuation matters, you probably shouldn't use this abbreviation in the first place.
****
