The correct answer is option C. Three pyramids RISE from the plateau, and the sphinx SEEMS to stand guard.
In the first case, the verb is plural because it has to agree with the subject (three pyramids). On the second part of the sentence, the suitable verb is seems, because the subject is singular: The sphinx. (Only one).
Subjects and verbs must agree with one another in number, if a subject is singular, its verb must also be singular. On the contrary, if a subject is plural, its verb must also be plural.