题目

The confirmed case in this building is said __________to the hospital already, but residents there still need to stay indoors to avoid being infected. A . to be sent B . to have been sent C . having been sent D . sent 答案：B如图是初中化学常见物质间的转化关系，（反应条件和部分产物已略去），其中C为既不溶于水也不溶于酸的白色沉淀，D、E、I均为气体，X为黑色固体，Y为红色固体，请回答下列问题：（1）物质C的化学式为______．（2）写出D→E的化学方程式______ 2CO