BP Why?

I suppose you are in F.6 or above.
So, I assume you know about dipole and electronegativity
and that a stronger intermolecular attraction would result in a higher bp.

BP Why? CH3OCH3 < CH3CH2Cl

CH3OCH3 is an ether
The group on two sides are just the same.
So, the dipole of the molecule will not be high.
On the contrary, Cl is more electronegative than C
So, CH3CH2Cl is more polar. Thus, the intermolecular attraction is higher.

BP Why? CH3CH2NH2 < CH3CHO < CH3CH2OH

N is less electronegative than O
so, the =O group or the -OH group would make the molecules more polar
and hence the intermolecular attraction stronger.
i.e. CH3CH2NH2 has the lowest bp.
-O-H group allows a much stronger type of intermolecular attraction
which is called the Hydrogen bond.
Therefore, CH3CH2OH has the highest bp.