The problem justto be discussed at the class meeting tomorrow.A. referred isB. referred to

问题补充：

The problem justto be discussed at the class meeting tomorrow.

A. referred is

B. referred to being

C. referring to is

D. referred to is

答案：

@@A. referred is@@B. referred to being@@C. referring to is@@(答案)D. referred to is

解析：本题的关键在于理解句子结构： referred to 在句中作定语，修饰名词the problem,而谓语动词为is， to be discussed是它的表语，be to do表示将来的动作。