Which of the following collections is a set?

1. Collection of all tasty fruits

2. Collection of all good football players of your school

3. Collection of all months of a year

4. Collection of 5 most intelligent students of your class.

The method of representation used in the set A = {x | x is an even natural number less than 15} is called

1. Description method

2. Rule method

3. Roster method

4. none of these

If S = {x | x is a letter in the word AHMEDABAD}, then the cardinal number of S is

1. 9

2. 8

3. 7

4. 6

If A = {x : x ∈ N and x is an odd prime number less than 17}, then the cardinal number of A is

1. 8

2. 6

3. 5

4. none of these