我国研制的高压水流切割器的技术已达到国际先进水平，这种很细的高速水流一次可顺利切割26层牛皮，或2.3mm厚的钢板…如果在水中加入某种砂质磨料，在水的流速相同的情况下，可切割300mm的花岗石，或130mm厚的钢板…

请简要回答：

（1）高速水流为什么能切割坚硬的物体？

（2）为什么加入砂质磨料后，在流速相同的情况下切割能力大大提高了？

I have been constantly advised my students not to be sidetracked by things that seem to be glamrous but actually energy consuming and unfruitful.

A. suggested my students not be
B. expostulated my students on not being
C. frowned on my students upon being
D. beguiled my students into being