Answer:
The correct answer is pienso.
Explanation:
The best option to answer this question is in the present simple. This verb tense is used to express a habit, a routine or, as in this case, a hypothetical situation.
It is something that this person plans to do in the spring, so it has not yet happened, this way we can discard the option "pensó".
We can deduce that the sentence refers to a single person since it contains the word "conmigo".
Next I will write the verb Pensar conjugated in the present simple for each person in Spanish:
yo pienso
tú piensas
él, ella, Ud. piensa
nosotros pensamos
vosotros pensáis
ellos, ellas, Uds. piensan
vos pensás
