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Combinatorics

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Number of Terms in an Expansion

COMBIN-KLVDVC

The expansion of:

$$(w+x+y+z)^7$$

...contains terms like $w^7$ and ${7\choose 1,\, 2,\, 1,\, 3}wx^2yz^3=420wx^2yz^3$. What is the total number of terms?

A

${7\choose 4}$

B

${10\choose 3}$

C

$2^7$

D

$4^7$

E

$7^4$

F

none of the above