¿conociste a muchas personas? a. si, conocí a muchas. b. comí solo.

This is the more logical option because the question means Did you meet many people? and the answer means Yes, I met many people. First of all, you start the sentence with an affirmation using the word sí. Then, you give a response saying that in fact you met many people. Finally, the dialogue is as follows:

- ¿Conociste a muchas personas?  

- Si, conocí a muchas.

smh i have no idea tbh

b.

explanation:

just because.

well, the b sentence is the only one that has sense.