Correct answer:
B estoy
Estoy is the conjugation of the verb estar for the first person singular in the simple present. Here the verb estar is being used as location, describing where I'm temporarily. On the other hand, the simple present tense is used to talk about habitual actions or routines. This tense is also used to describe things that happen now or in the near future. So I am at home an this is as follows:
Estoy en la cocina