—? dónde pongo la cesta? ud. en el suelo.
a. ponla
b. ponga
c. póngala
d. pongas

The answer is c, Póngala.

Explanation:

First, we have to find the Usted command form of the verb poner (as indicated by the question). Here's how we would do that:

1. Conjugate poner in the yo form (pongo).

2. Take away the "o".

3. Since it is an ER verb, add the AR verb ending for Usted (a, so it becomes ponga).

Now, we have the command, ponga. The last step is to attach the correct object pronoun. Since we are talking about "la cesta" (the basket), we would use the pronoun "la", which means "it". We would then attach la to the end of ponga to get "pongala". Finally, we would put an accent on the vowel of the syllable three from the end. Pongala can be broken into the syllables pon-ga-la, and the syllable three from the end is "pon". We would place the accent on the vowel in pon (o) to end up with "Póngala".