The entry of $t-DNA$ into plants is associated with which of the following?

Consider the following statements:
$I.$ In microinjection method,foreign $DNA$ is directly injected into the nucleus of an animal cell or plant cell by using microneedles or micropipettes.
$II.$ Microinjection method is used in oocytes,eggs,and embryos.
$III.$ Electroporation is the formation of temporary pores in the plasma membrane of a host cell by using lysozyme or calcium chloride.
$IV.$ In chemical-mediated gene transfer method,certain chemicals such as $CO_{2}$ help foreign $DNA$ to enter the host cell.
Which of the statements given above are correct?

In a bioreactor,through which system can a small volume of culture be withdrawn periodically?

Identify the correct statement.

Bioreactors are useful in

What is the criterion for the movement of $DNA$ fragments on an agarose gel during gel electrophoresis?