－Sunday is a public holiday children should get close to nature.－But most of them have s

问题补充：

－Sunday is a public holiday, children should get close to nature.

－But most of them have several lessons to attend.

A. where

B. which

C. in which

D. when

答案：

A. where

B. which

C. in which

(答案→)D. when

解析：句意：--星期天是个公共假日，这时孩子们应该接近大自然。--但是大多数孩子有几堂课要上。先行词是a public holiday，定语从句中缺少时间状语，用when引导定语从句，选D。