_____several times，but unfortunately，the boy still couldn’t smooth away the problem on his own.
#73673
A
Having been explained
B
The problem having been explained
C
The problem had been explained
D
Although the problem had been explained
推荐题目
He offered to drive me to the airport, I felt so grateful.
#69402
A
to whom
B
to which
C
for which
D
for whom
You may easily lose your way in Shanghai ______ you don’t have a map or a guide.
#41381
A
until
B
unless
C
though
D
if
Mr. White didn’t understand __________ made his wife so upset this morning.
#66608
A
what was it
B
why was it that
C
why it was that
D
what it was that
The researchers found clear and convincing evidence _______ happiness is the key when it comes to better health and longer lives.
#69037
A
where
B
whether
C
how
D
that