it travels 300000km a second是什么意思

it travels 300000km a second是什么意思 it travels 300,000 kilometres a second是什么意思 Light travels 300,000 kilometres a second the()thing in the universe is light,it travels at 300000 km a second是什么意思 a train travels 70 feet in 1/10 second.At this s light travels是什么意思? It goes at 30kilometers a second i have a second shot at it “in a second”what does it mean? run a second print中的run是什么意思 second是什么意思?