The intermolecular attractive forces vary in the order

If we see the order of boiling point given in the question then it will be in the order of: 

water $\left(100°C\right)>$ ethyl alcohol $\left(78.5°C\right)>$ diethyl ether $\left(34.6°C\right)$
Now,  if the intermolecular forces are more then there will be more attraction between the particles.it means that the attraction will not let  the particle to separate from each other and will not let escape in vapour phase, and due to which the vapour pressure will increase and hence, the boiling point will increase. Hence, we can say that if there are more intermolecular forces present then the boiling point will be more.  Intermolecular forces are directly proportional to boiling point.

Hence, the correct option is (B) .