问题
选择题
He failed in the English speech contest, ________ he did his best to prepare for it.
A．though
B．but
C．because
D．so
答案
答案：B
题中句意，转折应用but
搜题请搜索小程序“爱下问搜题”
He failed in the English speech contest, ________ he did his best to prepare for it.
A．though
B．but
C．because
D．so
答案：B
题中句意，转折应用but
深龋，充填治疗一段时间后脱落。可能有以下几方面原因，除了（）。