Only after they had completed an exhaustive study __________ how to adapt the technology to the needs of our company.

Complete the following sentence by choosing the phrase with the best word order from the options given.

Only after they had completed an exhaustive study __________ how to adapt the technology to the needs of our company.

A. did they understand to begin
B. did they begin to understand
C. they did begin to understand
D. to understand did they begin

Answer - C