上海市2015
高考英语阅读、短文语法填空精练（12）答案（四月）
阅读理解。阅读下列短文, 从给的四个选项 (a、b、c和d) 中, 选出最佳选项。
today, ultrasonic(超声的) waves are being put to work in laboratories and factories. if an ultrasound generator is placed in a liquid, the waves move the liquid back and forth hundreds of thousands of
