I'm in preference of D (of what).
When putting "that" in the sentence, it doesn't sound right when speaking the sentence out. And right after the comma, is it ok to put "that" at such a place?
I think "three times the price (get rid of the middle part) of what the drug maker charges for another pill...", then the "what" brings out the remaining of the sentence pretty smoothly.
No significant evidence to proof why it's right, but it does sound much better than "that" in my opinion. |