First of all, you need to know what the sentence above means.
"In general, to enter a car and unlock it, you need ___."
The options are llaves (keys), antenas (antennas), espejos (mirrors), and tanques (tanks).
So obviously, based on the context, the correct answer is going to be llaves.
I took spanish for a year and a half but I'm pretty sure its 'we' love (: