Only when home that he had left his bag in the taxi he had taken.A. he returned; did he r

问题补充：

Only when home that he had left his bag in the taxi he had taken.

A. he returned; did he realize

B. did he return; did he realize

C. he returned; he realized

D. did he return; he realized

答案：

(答案→)A. he returned; did he realize

B. did he return; did he realize

C. he returned; he realized

D. did he return; he realized

解析：考查倒装。Only + 状语从句，从句不倒装，主句的主谓要倒装，，故选A。