单选题
1.——There were already five people in the car but they managed to take me as well.
——It ______ a comfortable journey.
A.can't be
B.shouldn't be
C.mustn't have been
D.couldn't have been
正确答案：D
答案解析：由题意可知被猜测的时间是过去，有客观事实根据there were already five people……take me as well，猜测语气要求最强，所以正确选项是D。