1. This depends on the precise radio- frequency of the 21- cm wavelength, or 1420 megacycles per second .
    这种方法依靠21厘米波长或每秒1420兆周的精确无线电频率。

2. This depends on the precise radio- frequency of the 21- cm wavelength, or 1420 megacycles per second .
    这种方法依靠21厘米波长或每秒1420兆周的精确无线电频率。

3. This depends on the precise radio frequency of the 21-cm wavelength, or 1420 megacycles per second.
    这种通迅联系要靠21厘料波段，即每秒1420兆周的精确无线电频率。

4. Such undertakings require the precise planning and foresight of military operasions.
    此举要求有军事行动般的密周部署和预见。

5. Such undertakings require the precise planning and foresight of military operations.
    这种活动需要有军事行动般的周密布署和预见能力。

6. I can´t give you a precise date.
    我无法告诉你确切的日期。

7. It sounds legal and precise, but examine it and it turns out to be ridiculously broad.
    它听上去很符合法律，也很明确，但仔细查看一下，这问题就宽泛得荒唐可笑。