Which particles can pass through a semipermeable membrane?

At $27^{\circ} C$,the osmotic pressure of a solution containing $4 \ g$ of a non-electrolyte solute in $1.0 \ L$ of solution is $0.4 \ bar$. The molar mass of the solute in $g \ mol^{-1}$ is :
$(R=0.083 \ L \ bar \ K^{-1} \ mol^{-1})$

The pressure required for the reverse osmosis is quite high. For this,which of the following membranes is used?

When two solutions $X$ and $Y$ are separated by a semi-permeable membrane and the solvent flows from $Y$ to $X$,then:

The process of getting fresh water from sea water is known as

$3 \ mL$ of solution was made by dissolving $20 \ mg$ of protein at $0^{\circ} C$. The osmotic pressure of the resulting solution is $3.8 \ torr$. The molecular weight of the protein is approximately $(g/mol)$