Are you still upset ___ what I said to you yesterday?
Choose the appropriate preposition to fill in the blank.
A) with
B) by
C) about
D) None of these

Hint: A preposition is a word or a set of words that joins a noun or pronoun to construct a phrase that functions as an adverb, adjective, or noun. For example, "with" in "the house with the crimson door" is a preposition.

Complete answer:
Some verbs and adjectives have a preposition attached to them. Commonly used verb + preposition combinations are: about, at, from, for, in, of, on, to, with, etc.

Let us analyze the given options:
Option (A): with- “With” is a preposition of time. To describe where things are, we use the phrase with. Example- We left your package with your next-door neighbour because you were out when we called. Therefore Option A is incorrect, as the above-mentioned sentence doesn’t describe a preposition of time. “With” also establishes a relationship between things and people.

Option (B): by- The preposition ‘by’ is used to describe how or in what manner something is done. It's used to show who or what does, creates, or causes something, usually after a passive verb. “By” is a preposition of time and place, Example: She said she will be here by 5 p.m.
Hence we cannot use by in our sentence as it is inappropriate.

Option (C): about- About can be used in a number of manners as a preposition followed by a noun, adverb and after the verb ‘to be’. The most relevant meaning of ‘about’ as a preposition is "related to" or "on the subject of." Since it shows a connection between the adjectives. Hence, this option is correct as the speaker is asking whether the person is still upset on “the subject of” what he/she said.

Option (D): None of these: This option is incorrect as the sentence takes a preposition after the adjective ‘upset’.

Therefore, the correct answer is option ‘C’ i.e, Are you still upset about what I said to you yesterday?

Note: While working with prepositions keep in mind that-
- A noun or pronoun must always come after a preposition. The object of the preposition is that noun.
- Prepositions should rarely be used at the conclusion of a sentence since they must be followed by a noun and have an object. However exceptions apply.