Which statement is most appropriate for plant tissue culture?

In which method do cell clusters differentiate to form small,specialized cell groups?

What is the use of $Agar-Agar$ gel?

Reproducing new plants by cells instead of seeds is known as

Both in callus and suspension cultures,the commonly used auxin is

Read the following statements:
$I.$ Colostrum is recommended for newborns because it is rich in antigens.
$II.$ Chikungunya is caused by a Gram-negative bacterium.
$III.$ Tissue culture has proved useful in obtaining virus-free plants.
$IV.$ Beer is manufactured by the distillation of fermented grapes.
How many of the statement$(s)$ is/are correct?