they,the tree,sing,now,under.用现在进行时连词成句

问题描述:

they,the tree,sing,now,under.用现在进行时连词成句
没有"be"动词,怎么办?是不是故意不给的?

这套题有问题 少了are.
应该是They are singing under the tree now.他们现在在树下唱歌
或:Now they are singing under the tree.