Here are the answers to your questions:
Question 1 A) Which sentence correctly uses hyphenation conventions?
- Correct Answer: The smile appeared under the salt-and-pepper mustache.
Question 2 A) Which sentence correctly follows punctuation conventions?
- Correct Answer: However, the ice cream has very few ingredients. (Note: There is a minor error in 'its' in the first option; it should not have an apostrophe, and 'Boulder, Colorado' needs a comma.)
Question 3 A) Which sentence correctly uses the word they're correctly?
- Correct Answer: They’re currently studying the technique of underpainting.
Question 4 Which proposed edit correctly addresses the comma splice in the original sentence?
- Correct Answer: The argument against constructing a new highway is compelling; it will disrupt local ecosystems and water tables.
Question 5 A) Which sentence includes a comma splice?
- Correct Answer: Cell phones should be permitted in schools, they can function as an educational tool.
If you have any further questions or need clarification, feel free to ask!