since 时间的时态,什么时候用现在完成时,什么时候用现在完成进行时she_______in the elementary school since she graduated from college in 1990.a/ taught b/ has been teaching c/ was teaching d/ has taught
问题描述：
since 时间的时态,什么时候用现在完成时,什么时候用现在完成进行时
she_______in the elementary school since she graduated from college in 1990.
a/ taught b/ has been teaching c/ was teaching d/ has taught
答