Not Only__ But Also

Sapana wrote:** Spoiler Alert*** This question is fron Kaplan practice test. I could not hide the answers , they are in the question. Please take a look at this question and give me some direction to solve it.
Thank you!

The idiom "not only x but also y" is used to show that both items, x and y, are used in the same sense to support or emphasize each other. E.g., Sapana went to the shopping complex not only to purchase grocery items but also to dine in a Chinese restaurant.

However, the intended meaning of the sentence at hand requires a contrast in the later half of the sentence. So, the use of this idiom is inappropriate here.

We should use normal contrast word "but/but also" to show this contrast.

Of course there are other mistakes in the remaining choices, but this usage is glaring wrt to intended meaning.

D gets it correct by keeping the right tense and using the right connector "but it also" to show contrast.