He got down to writing the letter as soon as he returned from his walk.
He got down to writing the letter as soon as he returned from his walk.
A. No sooner had he returned from his walk when he got down to writing the letter.
B. Not until he returned from his walk did he get down to writing the letter.
C. Only after he had returned from his walk did he get down to writing the letter.
D. Hardly had he returned from his walk when he got down to writing the letter.