问题

This exercise is ________ difficult _________ .
A:so , that few of us can do
B:such , that few of us can do it
C:such , that few of us can do
D:so , that few of us can do it;
B:such , that few of us can do it
C:such , that few of us can do
D:so , that few of us can do it;
正确答案是: