Listen again to part of the lecture, then answer the question.
再听一遍这个演讲中的一小节，然后回答问题。
What do you need to do to that water besides put fertilizer in it?
除了在水里加入肥料还要对水做些什么？
Anyone ever actually tried to grow plants in water?
有人试过在水里种植物吗？
You must bubble water through it. Bubble gas through it. I'm sorry, you must bubble gas through it.
你得往里面充入水。充入气体。
So, gas, you have to bubble through.
说错了，是充入气体。所以你得往里面充气。
Why does the professor say this:
教授为什么说：
I'm sorry, you must bubble gas through it.
说错了，是充入气体。