Exactly______ the potato was introduced into Europe is uncertain, but it was probably around 1565.
#30010
A
whether
B
why
C
when
D
how
推荐题目
Don’t start reading a book _____ you find that it’s one you can read with ease and understanding.
#32304
A
when
B
if
C
unless
D
Though
In rugby（橄榄球），the ball is usually carried forward by players, ______kicking is permitted.
#33601
A
so
B
in case
C
so that
D
though
People living in the desert choose to keep their ancient lifestyles and customs, _______people in cities throw away their cultural traditions.
#31532
A
when
B
if
C
unless
D
while
The point is not who said the words, _________ they are true or not.
#79838
A
but whether
B
and whether
C
but how
D
and how