Which of the following are sets ? Justify your answer.

The collection of all boys in your class.

Which of the following sets are finite or infinite.

The set of months of a year

List all the elements of the following sers :

$D = \{ x:x$ is a letter in the word $"\mathrm{LOYAL}" $ $\} $

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

$\{1,2,5\}\subset A$

Make correct statements by filling in the symbols $\subset$ or $ \not\subset $ in the blank spaces:

$\{ x:x$ is a circlein the plane $\} \ldots \{ x:x$ is a circle in thesame plane with radius $1$ unit $\} $