Which of following is true about the capital contributions of members to an LLC?

Question

a) Capital contributions must be made in the form of Cash.
b)An unfulfilled promise to make a capital contribution is generally unenforceable.
c)Members are required to make equal contributions in order to maintain their limited liability.
d)A promise by a member to contribute services is excused if the member is unable to perform the particular services promised.
e)A member who promised to make a capital contribution is not discharged from the promise if the member dies without having made the contribution.

i beleive it is b, because partnership should be about each other advantages. what you think