Opticon
内髓
🗣️ 情景例句
I'm kind of excited about going now.
我现在就想去了。
Rivers need a spring.
大河要有源头。
This depends on the precise radio frequency of the 21-cm wavelength, or 1420 megacycles per second.
这种通讯联系要靠21厘米波段，即每秒1420兆周的精确无线电频率。