Correct Option: A

Let us look at the look phrases. If you look after someone, you do what is necessary to keep him healthy, safe, or in good condition. If you look after something, you are responsible for it. It is your duty to see that it functions all right. If you look ahead you think about what is going to happen in the future; you make plans for the future. On the contrary, if you look back you think about things that happened in the past. If A looks down on B, A considers B to be inferior or unimportant. If you look forward to something that is going to happen, you want it to happen because you think you will enjoy it. If you look into a problem you try to find out about it; you examine the facts related to the problem. If you look on while something happens, you watch it happening without taking part yourself. If you look up a fact or a piece of information, you find it out by looking in a reference book, list etc. If you look up to someone, especially someone, older than you, you respect and admire him.
The correct word is filled in the above given sentence :-
She was a devoted wife and looked after her husband very well.
Hence , option A is correct word .