It was in the small house _______ was built with stone by his father _______ he spent his childhood.

A．which , that

B．that , which

C．which , which

D．that ,where

饭前、便后洗手，这些行为属于（　　）

A．控制传染源

B．消灭病原体

C．切断传播途径

D．保护易感人群