单项选择题
A．and B．but C．yet D．so
A．a scientist as well as a naturalist B．a naturalist but not a scientist C．no more than a born naturalist D．first of all a scientist
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