cars and buses can only move slowly when there is a lot of this on the roadcars and buses can only move slowly when there is a lot of on the roadscars and buses can only move slowly when there is a lot of this on the roads中的this指什么？选项为：swans，traffic，a book，a lamp，chopsticks。比如举个例子：you take it when you are not feeling well,which helps you feel better.答案是medicine（药）.再举个these insects have beautiful wings and fly from one flowers to another.答案butterflies。
问题描述：
cars and buses can only move slowly when there is a lot of this on the road
cars and buses can only move slowly when there is a lot of on the roads
cars and buses can only move slowly when there is a lot of this on the roads中的this指什么？选项为：swans，traffic，a book，a lamp，chopsticks。比如举个例子：you take it when you are not feeling well,which helps you feel better.答案是medicine（药）.再举个these insects have beautiful wings and fly from one flowers to another.答案butterflies。我觉得选项中没有对的，（不是翻译啊）
是traffic。谁先回复我给谁采纳为最佳答案
答
当有很多时汽车和公共汽车只能慢慢地移动时在公路上行驶
答
ice , snow , water 都可以吧。
答
traffic 啦,路上交通堵塞时车得慢慢走,就是这个意思了
答
当公路上有很多汽车和公共汽车时。它们只能缓慢行驶。