【简答题】New inventions make old ones ____obsolete____. For instance, because of the compact disk, the phonograph record is now outdated. ____
【单选题】The purpose of new inventions is _______ life more difficult, but to make it easier.
【单选题】The area of a de Laval Nozzle is directly proportional to the ratio v/V, where v is the flow velocity and V is the specific volume.
【简答题】Which quantity does the area of velocity-time graph represent?
【简答题】Write the synonym of the italicized word in the space provided New inventions make old ones obsolete. For instance, because of the compact disk, the phonograph record is now outdated. _______________.
【单选题】Industrial leaders are Worried lest new inventions make their plants unprofitable to operate they therefore wish to protect themselves against possible ______.