1. I met Tom in the park yesterday.

Question

2. It was I that met Tom in the park yesterday.

3. It was I who met Tom in the park yesterday.

(What is the part of speech of 'that' in Sentence 2? Can we use 'who' instead of 'that'? Can we omit 'that'?)

4. It was in the park that/when I met Tom yesterday.
(Can we use 'when' instead of 'that'? Are both the same?)

Answer 1

2, 3, and 4 are awkward and too wordy. The first sentence is much better.

In sentence 2 "that" is a pronoun, but is not correct. When referring to a person, we use "who."

4. "That" is o.k., but "when" is wrong because it means time, not location. You could use "where" instead of "that."