—By       local farmers, we hope        them improve their lives.

—I think it’s a good idea.

A．train; help

B．training; helping

C．training; to help

D．train; helping

非线性失真指标是衡量有线电视系统质量好坏的最重要的指标，其中互调失真用C/CTB和（）来衡量。