If A = {5, 8, 10} and empty set ϕ. Then ϕ - A is equal to :

1. A

2. ϕ

3. {0}

4. none of these

If set A = {x : x ∈ W and 0 < x ≤ 4}, then set A is equal to :

1. {0, 1, 2, 3}

2. {0, 1, 2, 3, 4}

3. {1, 2, 3, 4}

4. none of these

The elements of the set {x : x ∈ Z and x² ≤ 9} are :

1. 3 and -3

2. {-3, -2, -1, 0, 1, 2, 3}

3. -2, -1, 0, 1 and 2

4. -3, -2, -1, 0, 1, 2 and 3

If A and B are two equal sets, then A - B is equal to :

1. A

2. B

3. {0}

4. { }