* We will be: Nous serons
Let's break down why the other options are incorrect:
* Fasse je suis serai: This doesn't make grammatical sense in French. "Fasse" is the subjunctive form of "faire" (to do/make), and the rest of the phrase doesn't follow a coherent grammatical structure.
* Que nous fassions: This means "that we do/make" and is in the subjunctive mood. It's not the same as "we will be."
Remember:
* Ser is the future tense of the verb "être" (to be) in the third person plural.
* Nous is the pronoun for "we" in French.
Therefore, "nous serons" is the correct way to say "we will be" in French.