Alfonso explica al médico sus a. recetas c. espaldas b. pastillas d. síntomas

If you feel bad and go to the Doctor, normally you will be asked about your symptoms (síntomas) and you will have to explain them. After that and some examinations or tests, the Doctor will give a diagnosis.

Therefore the complete sentence is:  

Alfonso explains his symptoms to the doctor

Note this is a sentence written in present tense with the 3rd person in singular he (él), which is Alfonso.

The options recetas (recipes or prescriptions), espaldas (backs) and pastillas (pills) do not match with the context of the sentence and are incorrect.

igualmente (likewise) or el gusto es mio (the pleasure is mine)