Verb agreement with "what"

This came up when reviewing a written English exercise, and I realized that I don't entirely trust my intuition on the answer.

Which of the following is correct? Or are both valid? (Or is it strongly advisable to rewrite the sentence in some other way?)

1. "I see what appears to be a man and his son."

2. "I see what appear to be a man and his son."

Solution 1:

Both are correct but infer different meanings. Context is important here.

The first describes a "man and his son" as a logical unit. Given the nature of the relationship it's not incorrect.

The second describes "a man" and "his son" in a literal, observational sense, as two distinct individuals.

Solution 2:

The former. You are describing a single sight, so the singular form is used. Correct forms are:

• I see what appears to be a man.
• I see what appears to be two men.
• I see two things that appear to be the same man.
• I see two things that appear to be men.
• My problems appear to be difficult and frightening.
• My problem appears to be difficult and frightening.