State whether the following set is finite or infinite:
The set of lines which are parallel to the $x$-axis.

If $Q = \{x : x = \frac{1}{y}, y \in N\}$,then which of the following is true?

Which of the following pairs of sets are equal? Justify your answer.
$A = \{ n : n \in \mathbb{Z} \text{ and } n^2 \le 4 \}$ and $B = \{ x : x \in \mathbb{R} \text{ and } x^2 - 3x + 2 = 0 \}$.

Let $A = \{1, 2, \{3, 4\}, 5\}$. Which of the following statements is incorrect and why?
$\varnothing \subset A$

Decide,among the following sets,which sets are subsets of one another:
$A = \{ x: x \in \mathbb{R} \text{ and } x \text{ satisfies } x^2 - 8x + 12 = 0 \},$
$B = \{2, 4, 6\}, C = \{2, 4, 6, 8, \dots\}, D = \{6\}$

Consider the sets $\phi, A=\{1,3\}, B=\{1,5,9\}, C=\{1,3,5,7,9\}$. Insert the symbol $\subset$ or $\not\subset$ between the pair of sets: $A, \ldots B$.