人类的DNA是条很长的链，最短的是22号染色体也长达30000000个核

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问题填空题

人类的DNA是条很长的链，最短的是22号染色体也长达30000000个核苷酸，这个数字用科学记数法可表示为______个．

答案

30 000 000=3×10⁷．

故答案为：3×10⁷．

选择题

26.—Were the audience allowed to join in the play?

—Yes, the actors_______to satisfy the audience were successful.

A．who it was the duty

B．of which the duty was

C．whose duty it was

D．whose was the duty

单项选择题

航空汽油设备上的标志一般是：（）.

A.红底白字

B.黑底白字

C.黄底黑字

D.黄底红字