He couldn’t comprehend the details of the document.

emphasise
grasp
condense
implement

The correct answer is B. grasp.

To grasp something is to understand it fully. In this case, the man could not understand the details of the document.

The other options are incorrect because:

  • To emphasize something is to stress its importance.
  • To condense something is to make it shorter.
  • To implement something is to put it into effect.