Bunuel wrote:

How many different ways can two basketball teams be formed from 7 friends?

(1) Any combination of players is allowable except those with one or two members.

(2) All teams must have at least 3 players.

I’ll start from the second one.

(2) All teams must have at least 3 playersThe only way we can actually divide 7 players into groups with at least 3 players is when one group will consist of 3 players and another one from 4. We can’t make team from one left player so he/she should be added to one of the 3-player teams.

\(\frac{7!}{4!3!}\) Sufficient.

(1) Any combination of players is allowable except those with one or two members.This is another way to say that team should consist of at least 3 players. Sufficient.

Answer D