What is dark but made by light?
c s g h j f k l m e o i h n q d s w b d r p o a
knee ------------ light
（猜一個英文片語）
What can be measured but has no length, width or thickness?
This is as light as a feather, yet no man can hold it for long. What is it?(six letters)
What has teeth but cannot eat?
city light有兩個不同的玻璃杯（兩個杯子都接近圓柱體），兩個都裝有一定量的水，A杯的水位比B杯高五厘米。A杯的底部沉沒著一個石塊，當石塊被取出並放入B沉沒后，B杯水位上升了五厘米，並且比這時A杯的水位還高十厘米。則得知A杯與B杯的底面積之比為多少？
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