We can’t do anything before ______. ?

The phrase "We can’t do anything before ______" requires a verb form in the blank that expresses an action that must happen in the future. In this context, the correct choice is "A) the doctor comes."

This structure uses the present simple tense "comes" to indicate a scheduled or expected future event. It suggests that our ability to act is contingent upon the doctor arriving. This is a common use of the present simple to denote future meanings when discussing timetables or events that are certain to occur.

On the other hand, the other options do not fit the context appropriately. "B) the doctor didn’t come" refers to a past event that has already happened and conveys a completed action, which makes it irrelevant for our future plans. "C) the doctor will come" is grammatically correct but is less direct than the present simple form in this particular construction. Lastly, "D) the doctor doesn’t come" uses the present simple in a negative form, which implies an ongoing action and introduces ambiguity, making it unsuitable for indicating a prerequisite for future action. Therefore, "A) the doctor comes" is the most logical and grammatically appropriate choice.