Health problems are closely connected with bad eating habits and a________of exercise.
A:limit
B:lack
C:need
D:demand
谚语:“大河有水小河满,大河无水小河干。”这句话生动说明( )
蝙蝠能够飞行,但不属于鸟类,而属于哺乳类.主要理由是蝙蝠( )
亚洲是我们生活的大洲,它地域辽阔,文化多样.读图,回答下列问题: