What is the purpose of the sizeof operator in C$?$

Question $3$ options:

$1)$

To allocate memory dynamically.

$2)$

To get the size of a variable or data type.

$3)$

None of the other options.

$4)$

To resize the previously allocated memory block.

$5)$

To free the memory previously allocated by malloc$()$ or calloc$().$