在野外找到水源，不干净的水至少应煮多少分钟。（） A.3 B.10 C.15 D.2

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问题单项选择题

在野外找到水源，不干净的水至少应煮多少分钟。（）

A.3

B.10

C.15

D.20

答案

参考答案：B

选择题

( ) 1.	a. Winter is cold. There is ice and snow.
( ) 2.	b. Spring is warm and rainy. The flowers bloom.
( ) 3.	c. It is cool and windy in fall. The wind blows the leaves off the trees.
( ) 4.	d. It is hot in summer. I wear my sunglasses.

单项选择题

牙源性角化囊肿也是( )

A．萌出囊肿

B．始基囊肿

C．含牙囊肿

D．鼻腭管囊肿

E．婴儿龈囊肿