The mixture of elements in the air can be thought of___a solution of gases.
问题描述：
The mixture of elements in the air can be thought of___a solution of gases.
The mixture of elements in the air can be thought of___a solution of gases.
A,to B,as C,over D,about
答
B,as （ can be thought of as 是情态动词的被动语态）
think of sth as sth 把.看做.can be thought of as 怎么能看出是情态动词的被动语态呢？把原句改为主动句是We can think of the mixture of elements in the air as a solution of gases.