The Turners consider ____ a computer, which is commonly considered _________ a great help in our work and study.

A．to buy; to be

B．buying; to be

C．to buy; being

D．buying; being

如图所示，细绳MO与NO所能承受的最大拉力相同，长度MO＞NO，则在不断增加重物G的重力过程中（绳OC不会断）

A．ON绳先被拉断

B．OM绳先被拉断

C．ON绳和OM绳同时被拉断

D．因无具体数据，故无法判断哪条绳先被拉断