10. Almost anyone who has ever thought of becoming an ape would imagine himself/herself as prepared to do what it takes to become a good boyfriend or girlfriend.

1) There is no comma after "ape." "who has ever thought of becoming an ape" is a relative clause that refers back to "anyone;" therefore, there is no need to put a comma between the subject and the verb.

2) "Anyone" is a singular indefinite pronoun. Therefore, "themselves" needs to be singular. It could be changed to "himself," "herself," or "himself/herself."