HF的工作频段是多少？A、0.2-2.99999MHZ B、2--29.9999MHZ_爱下问搜题

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问题单项选择题

HF的工作频段是多少？

A、0.2-2.99999MHZ

B、2--29.9999MHZ

C、2-299.999MHZ

D、0.2-299.999MHZ

答案

参考答案：B

选择题

情景交际我最棒，根据情景选择最佳答案。

1. A letter is __________ the table. [ ]

A. in

B. on

C. under

2. —Where is Xiaoyong?

—__________[ ]

A. He's on the box

B. He is on the bed.

3. —What is this?

— __________.[ ]

A. It's on the box.

B. It's a box.

4. He is swimming __________ the lake. [ ]

A. on

B. in

C. under

5. —__________?

—It's on the chair.[ ]

A. What is it

B. Where is the apple

C. How is the apple

6. She often __________ in the park. [ ]

A. flies kites

B. swims

C. walks

单项选择题

蒸制后既软化药物、破坏了酶、便于切片，又保存了有效成分的药材是

A．地黄
B．黄精
C．何首乌
D．黄芩
E．玉竹