若要放置总线,首先应如何操作? ( )<br/> A、A. 按<img src="https://static.zxtiku.com/wangke/imgs/topic/60e8e8e767962ddc5c20963dc0931f55.jpg"/>钮 <br/> B、B. 按<img src="https://static.zxtiku.com/wangke/imgs/topic/bf82f5b98868c0c7fc6a9a0524e3ea21.jpg"/>钮<br/> C、C. 按<img src="https://static.zxtiku.com/wangke/imgs/topic/525a84d6e862df26c06ba929670b3e59.jpg"/>钮 <br/> D、D. 按<img src="https://static.zxtiku.com/wangke/imgs/topic/59bbb0ff4cd3e3a9e5e3f71b2168b3cc.jpg"/>钮