Binding promise?

Question

which one of these is not an essential ingredient of a binding promise?

consideration
legality of object
manifestation of mutual assent
a writing

Answer 1

"writing" is the correct answer.

An oral offer (promise) is binding if accepted.

An offer (promise) is not binding until accepted.

Offer + acceptance = mutual assent (at least for the purposes of whatever class you're taking. What class is this? Intro to business law?)

Answer 2

Manifestation of mutual assent is not an element of a binding promise.