单项选择题
A．As B．Like C．Since D．Because
A．products should be made with less cost but higher efficiency B．products should be sold at low prices in large quantity C．products should be sold at high prices in large quantity D．standards must be established in his plants
A．it is one thousand times more precise than microwave radar B．it provides precise measures of the velocity of space vehicles C．it is a new system of radar D．it can measure the movement of a spaceship less accurately than a microwave radar