--Comeputers are so useful.They can do almost everything!--Yes.But they ___ what to do
问题描述：
--Comeputers are so useful.They can do almost everything!--Yes.But they ___ what to do
--Comeputers are so useful.They can do almost everything!
--Yes.But they ___ what to do
A must be told
B has to be known
C．has to be known
D．will know
答
A..BC应该是have to 因为主语是they..而且be known是被知道,应该是know.根据语境不应用将来时,所以不选D