主要原因是会议期间个体不能随意走动，虽然接触距离比较近，但相互不交谈。

The main reason is that individuals cannot move around freely during the meeting, and although the contact distance is relatively close, they do not talk to each other. During the break and during the meal, the infection is caused by contact and conversation through droplets

The main reason is that individuals can't walk around at will during the meeting. Although the contact distance is relatively close, they don't talk to each other. The rest period and dining period are both contact and conversation, and the infection is carried out through droplets

The main reason is that individuals can't walk around freely during the meeting, but they don't talk to each other although the contact distance is relatively close. During the rest period and during the meal, the infection is caused by contact and conversation through droplets.