题目

For the first time in the history of the Beijing, Shanghai and Hangzhou marathons, fourteen blind runners competed in the Nov 6 Hangzhou Marathon this year with the assistance of personal guides. Each runner was supported by 4 or 5 volunteers. Among them was Yan Wei, from a running group called “Running in the Dark”, which specially provides training for blind runners.During trainings, blind runners are each accompanied by three volunteers. One volunteer is responsible for removing any obstacles（障碍物）on the road and controlling the pace. The secondvolunteer acts as a lookout for o下列图示的化学实验基本操作中，正确的是（ ）A．倾倒液体B．称量固体C．检验气密性D．加热液体