________ 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
The idea of fish being able to produce electricity strong enough to light a lamp is almost unbelievable, _____ several kinds of fish are really able to do this.
#34581
A
therefore
B
and
C
then
D
but
The job is great in terms of salary . It has its disadvantages, _______ .
#33823
A
though
B
however
C
even
D
therefore
—What are you going to do this afternoon?—I’ll probably go for a walk later on________it stays fine.
#31226
A
as far as
B
so long as
C
even if
D
as though
A number of high buildings have arisen _______ there was nothing a year ago but ruins.
#32241
A
when
B
where
C
before
D
until