According to the 'Unit membrane model',the thickness of the cell membrane is about: (in $nm$)

Given below are two statements.
Statement-$I$: Cell wall is freely permeable.
Statement-$II$: Plasma membrane is selectively permeable.
Choose the correct answer from the options given below with reference to the structure of root hair.

Which concept was proposed by the scientist Robertson?

In the fluid mosaic model of the plasma membrane:

The water-soluble materials pass through the proteins called

Explain: On what basis are substances transported by the plasma membrane/cell membrane?