________ several times，but he still doesn't know how to do it correctly.
#30467
A
Although I've taught him
B
I've taught him
C
Having been taught
D
Having taught
推荐题目
(2010·新课标全国)Mary made coffee ________ her guests were finishing their meal.
#30450
A
so that
B
although
C
while
D
as if
It was some time _______ I realized the fact that I had been cheated by the salesman.
#31376
A
until
B
before
C
unless
D
since
She says that she’ll have to close the shop ________ business improves.
#30239
A
if
B
unless
C
after
D
when
-----Do you have a minute ? I’ve got something to tell you. -----OK, ___________ you make it short.
#32501
A
now that
B
if only
C
so long as
D
every time