[译] 共青团员们在河两岸植树。
[误] The League members planted trees on every side of the river.

[正] The League members planted trees on each side of the river.
[注] each 可以用来指两个或两个以上的人或事物，但是，every 却总是指三个或三个以上的人或事物，绝不能指两个。河流只能有两边，所以是 each side of the river。