(was + was) vs (was + is)
I was wondering what's the difference between these two sentences:
The person who was at the head of the demonstration is Ms. Tan.
The person who was at the head of the demonstration was Ms. Tan.
Solution 1:
Sentence 2 merely reports what has happened, whereas 1 suggests some present relevance. For example, a TV presenter might say ‘The person who was at the head of the demonstration is Ms. Tan and we’re delighted to have her on the show tonight.’
Solution 2:
Interpreting these two statements as possible responses to the question "Who was at the head of the demonstration?", you'd probably say "...is Ms. Tan" if Ms. Tan were either physically present at the time of the question, or was "metaphorically" present in some way (for example, the questioner had a short list of possible candidates, and wished to establish which one it was).
If Ms. Tan were not present, and wasn't specifically being thought of by the questioner as a possible/probable answer, you'd more likely say "...was Ms. Tan".