问题
单项选择题
进行示踪注水剖面测井时，应选用中、低毒性放射性同位素，其半衰期最好不超过（）天。
A、15
B、20
C、30
D、35
答案
参考答案：C
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进行示踪注水剖面测井时，应选用中、低毒性放射性同位素，其半衰期最好不超过（）天。
A、15
B、20
C、30
D、35
参考答案：C
The sun is shining and it’s very hot. 31 many people don’t want to go out after 32 . Mrs. West has to(不得不) 33 her father at the airport. Her father doesn’t feel well, he wants to see a 34 in the city hospital. Now she’s 35 in the street. There 36 no trees and she feels very 37 . But she’s too 38 and can’t walk fast(快). Suddenly she finds(发现) a 39 walking behind her. She gets angry and her face turns red. “Why are you walking 40 me, boy?” She asks strictly. “It’s cooler”. The boy answers.
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