The result of another study involved phone-use questionnaires shows that ______.

A．brain cancer patients don't incline to use cell-phones

B．cancer-free participants like to use cell-phones

C．significance of cell-phones

D．cancer-free participants seldom use cell-phones

如果空气中含有硫化氢气体，用光学瓦斯检定器测定瓦斯时，应再加一个辅助吸收管，管内装有（）可消除硫化氢影响。

A、生石灰

B、硅胶

C、碳酸钙

D、颗粒活性碳