问题补充:
Only when 30 years old to learn English.
A. was he; did he begin
B. he was; he began
C. he was; did he begin
D. was he; he began
答案:
A. was he; did he begin
B. he was; he began
(答案→)C. he was; did he begin
D. was he; he began
解析:考查部分倒装。Only+时间状语从句,放在句首时,后面主句要部分倒装,而从句不倒装。所以选C。