15. I was wearing a seatbelt. If I hadn’t been wearing one, I ____.
A
were injured
B
would be injured
C
had been injured
D
would have been injured
根据从句中用 if + 主语 + had done 的形式可知是对过去的否定，故主句应为 would/should/could/might + have done 的形式，D项符合题意。故正确答案为D。
if + 主语 + had done 的形式是对过去的否定。
虚拟语气结构理解不清致错。