He was asked to accelerate the pace of work.

Answer: Option B

accelerate : begin to move more quickly.
supervise : observe and direct the execution of (a task or activity).
slacken : relax.
control : the power to influence or direct people's behaviour or the course of events.
check : examine (something) in order to determine its accuracy, quality, or condition, or to detect the presence of something.


Antonym of accelerate is slacken