Question

1a. Did you know a famous animal-rights activist has criticized horseracing because of the dangers involved?
1b. Did you know a famous animal-rights activist have criticized horseracing because of the dangers involved?
my answer is A. could you please explain it to me?

Answer 1

A is right - subject-verb agreement

http://grammar.ccc.commnet.edu/grammar/sv_agr.htm

Answer 2

thank you