Which of the following are sets ? Justify your answer.

The collection of ten most talented writers of India.

Write the following sets in roster form :

$D = \{ x:x$ is a prime number which is divisor of $60\} $

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

$\{ 3,4\}  \subset A$

Let $A =\{1,2,3, \ldots \ldots, 10\}$ and $B=\left\{\frac{m}{n}: m, n \in A, m < n \text { and } \operatorname{gcd}(m, n)=1\right\} . $Then $n(B)$ is equal to :

Examine whether the following statements are true or false :

$\{ 1,2,3\}  \subset \{ 1,3,5\} $

Write the following sets in the set-builder form :

${\rm{\{ 2,4,8,16,32\} }}$