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.

Đáp án D

Dịch nghĩa: Anh ta ngồi xuống viết thư ngay khi đi bộ về.
Xét các đáp án:
A. No sooner had he returned from his walk when he got down to writing the letter. → Cấu trúc đảo ngữ với các cụm từ so sánh về thời gian: No sooner + had + S + P2 + than + S + Ved (nếu dùng no sooner phải có than đằng sau).
B. Not until he returned from his walk did he get down to writing the letter. → Mãi cho đến khi anh trở về sau khi đi bộ, anh mới xuống viết thư, sai nghĩa.
C. Only after he had returned from his walk did he get down to writing the letter. Chỉ sau khi anh ấy trở về sau khi đi bộ, anh ấy mới viết thư, sai nghĩa
D. Hardly had he returned from his walk when he got down to writing the letter. → Cấu trúc đảo ngữ với các cụm từ so sánh về thời gian: Hardly/Scarcely/Barely + had + S + P2 + when + S + Ved: ngay khi/vừa mới….thì….