The given sentence is: "You will not(a) get well until(b) you take medicine regularly.(c) No error(d)"
This sentence is a conditional sentence indicating the idea of an action being necessary to produce a particular result. The error in the sentence is related to the use of negative words in the conditional clause.
Therefore, the error is in part (b).
Identify the part of the sentence that contains an error:
"Neither the manager nor the employees ___ willing to accept the new policy."