What is the most appropriate answer to the following question? "¿adonde va emma? " a. vas a la casa. b. va a la casa. c. va al casa. d. va a el casa.

The question

¿Adónde va Emma?

(Where does Emma go?)

is written with the verb ir (to go) in present tense with the 3rd person in singular she, which is Emma.  

The conjugation of the Spanish verb ir for ella (she) in present is va (goes).  

This means, the option A is discarded.

Casa (House) is a feminine noun; hence it must be preceded by the article la.

Therefore, options C and D are discarded, as well, and the right answer is B:

or, (Ella) va a la casa

(She goes to the house)