If you tie down someone, you restrict his freedom in some way.

Correct Option: B

If you tie down someone, you restrict his freedom in some way.
The correct word is filled in the above given sentence :-
The battalion operating from the mountain was able to tie down three enemy divisions.

Common sense tells us that high saving rates should lead to (greater investment and therefore) “high” growth rates.

Correct Option: D

Common sense tells us that high saving rates should lead to (greater investment and therefore) “high” growth rates. But here it is “low”. This is a paradox
The correct word is filled in the above given sentence :-
India has the paradox of high saving and low growth rates.
Thus , required answer will be option D .

If you are even moderately interested in news, you must have heard of the NPT.

Correct Option: D

If you are even moderately interested in news, you must have heard of the NPT. It stands for Nuclear non-proliferation Treaty — a treaty which aims at halting the proliferation (increasing in number very quickly) of nuclear (atomic) weapons.
The correct word is filled in the above given sentence :-
Survival of mankind itself is in danger due to proliferation of atomic weapons.

The words “interdisciplinary” and “interaction” point to the working together (co-operation) of the various departments.

Correct Option: A

The words “interdisciplinary” and “interaction” point to the working together (co-operation) of the various departments.
The correct word is filled in the above given sentence :-
Nowadays there exists a spirit of co-operation among the various departments of the University. This has led to a number of interdisciplinary research publications due to interaction of various research groups.
Thus , required word will be option A .

As we can say that ,
If you highlight a point or problem, you throw greater light on it than on others.

Correct Option: D

As we can say that ,
If you highlight a point or problem, you throw greater light on it than on others. That is, you emphasise it or make others think about it.
The correct word is filled in the above given sentence :-
In his address to the teachers, the Vice-Chancellor highlighted certain measures being taken for improving the quality of college education.
Hence , required word will be option D .