Which of the following collection is set?

The collection of all letters of the English alphabet which precede $K$.

Which of the following collection is set?

The collection of all good athletes of India.

Which of the following collection is a set?

The collection of fat boys of your locality.

Which of the following collection is a set?

The collection of all those students of your class whose age exceeds $15$ years.

Rewrite the following statement, using set notations:

$a$ is an element of set $\mathrm{A}$.

1. $a\in \mathrm{A}$

$2.a\subset \mathrm{A}$

Write $1$ or $2$ as the final answer.

On rewriting the following statement, using set notations: $b$ is not a element of $A$, then $b\notin$ ......

Rewrite the following statement, using set notations:

$A$ is an empty set and $B$ is a nonempty set.

Rewrite the following statement, using set notations:

Number of elements in $A$ is $6$.

Rewrite the following statement, using set notations:

$0$  is a whole number but not a natural number.