无码高清视频|成人自拍视频|欧美成人午夜无码A片秀色直播|草美女视频网站|美女被操网站在线观看

單項選擇題

The population decreased from the 1840s until about 1970,largely because of().

A.a low birth rate 
B.a high death rate
C.a low employment rate 
D.a high emigration rate

微信掃碼免費(fèi)搜題