What subject pronoun that would replace this sentence Have Tomas and Susan seen the lizard?

The subject pronoun that would replace the sentence "Have Tomas and Susan seen the lizard?" is they.

Here's why:

* Tomas and Susan are the subject of the sentence, performing the action of seeing the lizard.

* They is a plural pronoun that refers to two or more people, making it the appropriate replacement for the subject.

So the sentence becomes: Have they seen the lizard?