Find ways to praise your children often, ________ you'll find they will open their hearts to you.[ ]

A. till  

B. or

C. and  

D. but

在全球致死的寄生虫病中，下列排第一位的是（）

A.疟疾

B.血吸虫病

C.阿米巴虫病

D.黑热病

E.囊尾蚴病