填空题

According to the normal ratio of ions in the air, how many negative ions are there in one cubic centimeter of air __________________.

【参考答案】

There are about 880 negative ones in it.
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A．Using cheques sometimes may embarrass the cheque holder.B．Cheques are valuable in themselves.C．Using cheques is always convenient for a cheque holder.D．Under no circumstances can a shopkeeper refuse to accept a cheque.
A．Using cheques sometimes may embarrass the cheque holder.
B．Cheques are valuable in themselves.
C．Using cheques is always convenient for a cheque holder.
D．Under no circumstances can a shopkeeper refuse to accept a cheque.
填空题
Where can we find ions according to the passage__________________.
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