Answer: a. Es mejor que vayas a la playa.
Explanation: The sentence is:
No sé si debo ir a la playa o al cine.
Which means something like:
I don't know if I must go to the beach or at the movie theater.
The options given are:
a) Es mejor que vayas a la playa.
b) Es mejor que vas a la playa.
c) Vé a la playa.
Where options a and b are almost equal, but "b" is not written correctly.
The difference between option a and c, is that a is a suggestion, and c is almost an order.
In this situation, the right option is the polite one, so the right option will be a.
