________ is known to us all is that smoking does harm to one’s health．
________ is known to us all is that smoking does harm to one’s health．
A.It
B.What
C.As
D.Which
答案及解析： B
________ is known to us all is that smoking does harm to one’s health．
A.It
B.What
C.As
D.Which
答案及解析： B