Answer:
A. Pienso
Step-by-step explanation:
Translation:
"Pienso": think
"Pienso" comes from the verb "pensar" which is conjugated in the present indicative tense for the first person of the singular "yo" (I) of Spanish.
"Penso" is not a word in Spanish.
"Piensa" is conjugated in third person of singular (she, he)
"Pensamos" is conjugated in second person of plural (we)