Section 301 of the 1988 Omnibus Trade and Competitiveness Act enables the United
States Trade Representative to single out a country as an unfair trader, begin trade
negotiations with that country, and, if the negotiations do not conclude by the United
States government's being satisfied, to impose sanctions.

A. by the United States government's being satisfied, to impose
B. by the United States government's satisfaction, impose
C. with the United States government's being satisfied, imposing
D. to the United States government's satisfaction, impose
E. to the United States government's satisfaction, imposing

OA: D

can someone explain why we can't use by?
and plz tell me how to use IMPOSE.

thank u so much!