Which of the following is a subset of every set?

Which of the following pairs of sets are disjoint?
$A = \{ x : x \text{ is an even integer} \}$
$B = \{ x : x \text{ is an odd integer} \}$

If $A = \{x \in R : x^2 - 5|x| + 6 = 0\}$,then find $n(A)$.

If $A = \{1, 2, 3, 4, 5\}$,then the number of proper subsets of $A$ is

An alternative equivalent circuit for the given circuit is:

The set $\{n(n+1)(2n+1) : n \in \mathbb{Z}\}$ is a subset of: