Let $A=\{1,2,\{3,4\}, 5\} .$ Which of the following statements are incorrect and why ?
$1 \in A$
Which of the following are examples of the null set
Set of odd natural numbers divisible by $2$
Write the following sets in roster form :
$D = \{ x:x$ is a prime number which is divisor of $60\} $
How many elements has $P(A),$ if $A=\varnothing ?$
Which set is the subset of all given sets