The number of distinct terms in the expansion of (x +2y - 3z + 5w - 7u)ⁿ is
a. n + 1
b. ⁿ⁺⁴C₄
c. ⁿ⁺⁴Cₙ
d. ((n + 1)(n + 2)(n + 3)(n + 4))/24