ANS:B - Digital-to-analog conversion

The question is asked in somewhat reverse manner.

At first sight when we read and come into mind that he is asking manipulation of data from analog to dital.

But all this is the game of words.

It is said in last word the domain I. E, digital domain means in actual we are practicing in digital domain and in that domain we are manipulating the analog data.

So from digital to analog is digital to analog conversion.

That's it.