Answer: (d)
Explanation:
Given 
There are six flavors of ice-cream that is chocolate, vanilla, strawberry, birthday cake, rocky road, and butter pecan
First ice-cream can be tasted in 6 different ways
Second can be in 5 ways 
similarly, remaining in 4, 3, 2 and 1 ways
Total no of ways are 

 Option (d) is correct.