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
网友回答
(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。