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

$\varnothing \subset A$

Which of the following are sets ? Justify your answer.

A collection of novels written by the writer Munshi Prem Chand.

Which of the following sets are finite or infinite.

The set of months of a year

Are the following pair of sets equal ? Give reasons.

$A = \{ x:x$ is a letter in the word ${\rm{FOLLOW }}\} $

$B = \{ y:y$ is a letter in the word $WOLF\} $

Match each of the set on the left in the roster form with the same set on the right described in set-builder form:

$(i)$ $\{1,2,3,6\}$ | $(a)$ $\{ x:x$ is a prime number and a divisor $6\} $ |

$(ii)$ $\{2,3\}$ | $(b)$ $\{ x:x$ is an odd natural number less than $10\} $ |

$(iii)$ $\{ M , A , T , H , E , I , C , S \}$ | $(c)$ $\{ x:x$ is natural number and divisor of $6\} $ |

$(iv)$ $\{1,3,5,7,9\}$ | $(d)$ $\{ x:x$ a letter of the work $\mathrm{MATHEMATICS}\} $ |