Which of the following does not require carrier molecules during transport through cell membranes?

Identify $(i), (ii)$ and $(iii)$ based on the provided diagram of carrier proteins in a membrane.

In a .....$A$..... both molecules cross the membrane in the same direction,in an ...$B$.... they move in opposite direction :
$A - B$

In cell transport,the difference between permeable transport and bulk transport relates to:

Choose the correct sentences for diffusion:
$(1)$ In diffusion,molecules move in a random fashion.
$(2)$ Diffusion rates are affected by the gradient of concentration.
$(3)$ Diffusion is a slow process and is dependent on a 'living system'.
$(4)$ Movement by diffusion is passive.

Facilitated diffusion in cells is brought about by . . . . . . in the cell membrane.