Could anyone kindly give me a quick confirmation for each of the following questions?
- "In 54° heat" : would you read it: "in fifty-four degree heat"?
- Do you pronounce the "s" in the word "genres" (even though it's a French word)?
- In an elevator, would you say "what (or which) floor" when you offer to push a button for somebody?
- Would you say " That (or those) twenty dollars was (or were) very useful"
- When a native speaker writes "Mr. Wilkins' car" would he/she actually say "Mr Wilkins's car" ? In other words, when you don't add an "s" after the apostrophe, would you pronounce it anyway?
I'd greatly appreciate it if you could answer at leat a couple of the above.
Thank you so much
Hey there! Hope I can be of some help:

It is uncommon to include the temperature after a preposition, but you would indeed pronounce the symbol while speaking.

You do indeed pronounce the s when saying "genres," although it sounds mighty weird!

"What floor" and "which floor" are both commonly acceptable in colloquy.

"Those twenty dollars were very useful." Since dollars is plural here, you want to make everything coincide. I will mention, though, that in the southern part of the United States, it is very common to refer to "dollars" as singular - for example: "I already spent that five dollars!" However, usually stick with the plural.

For all my years in English training, I can't recall for the life of me which is formally correct in "Mr. Wilkins'" versus "Mr. Wilkins's," but I know that both are acceptable in colloquy.

Good luck!
First let me thank you for the detailed explanations you provided. It was very kind of you to take the trouble to write back so promptly. As for question number one, however uncommon and awkward that noun phrase may sound, I read it in TIME magazine last month (December issue, page 65) so I was just wondering how to pronounce it. Quote :" Even in 54° heat, the Tomb Raiders sometimes ran patrols five times a day on four hours' sleep. Etc.etc." (so you would say 54 degree heat, i.e, no "s" after the word degree, right?)

Perhaps you might want to help me clear up another doubt. As you can see for yourself, I already asked this question, but I would appreciate an answer from a native speaker:
- IT'S US/YOU (plur)/THEM WHO... + plural or singular?: ex: It's us who have/has to pay.
- COLIN, would you pronounce it /kolin/ or /koulin/ ?(I've heard /koulin/ but dictionaries indicate /kolin/)
- DEBUTED should be pronounced /dei'biu:d/ or /dei'bju:tid/. I'd opt for the former.
Thanks for your time and dedication, Diamondkite.