Nosotros muy inteligentes.
a.
estamos
b.
somos

Nosotros somos muy inteligentes

Explanation:

Both conjugations are correct in their tense (present), the personal pronoun that they refer to (“nosotros”) and for being the translation of the verb “are” in English. However, the Spanish language offers two options for the verb “are”. The option “somos” (a conjugation of the verb “ser”) designates a more stable or permanent condition, whereas the option “estamos” (a conjugation of the verb “estar”) is usually used for a condition that you have or feel that is temporary.

In this case where the phrase can be translated as “we are very intelligent”, one assumes that the intelligent condition that we have, won’t change in a few minutes, days or weeks, but rather that it is something stable or permanent. Therefore “somos” is the correct verb to use.