OOA(Object-Oriented Analysis)模型由5个层次和5个活动组成,5个层次不包括 (33) ,5个活动不包括 (34) 。OOA在定义属性的同时,还要识别实例连接。实例连接是一个实例对象与另一个实例对象的 (35) 关系。 (33)处填()。
A. 主题层
B. 对象类层
C. 动态层
D. 结构层
Driving through snowstorm on icy roads for long distances is a most nerve-racking experience. It is a paradox that the snow, coming (1) gently, blowing gleefully in a high wind, all the while (2) down a treacherous carpet, freezes the windows, (3) the view. The might of automated man is (4) . The horses, the powerful electrical systems, the deep-tread tires, all go (5) nothing. One minute the road feels (6) ,and the next the driver is sliding over it, light as a (7) ,in a panic, wondering what the heavy trailer trucks coming up (8) the rear are going to do. The trucks are like (9) when you have to pass them, not at sixty or seventy (10) you do when the road is dry, but at twenty-five and thirty. (11) their engines sound unnaturally loud. Snow, slush and (12) of ice spray from beneath the wheels, obscure the windshield, and rattle (13) your car. Beneath the wheels there is plenty of (14) for you to slide and get mashed to a pulp. Inch (15) inch you move up, past the rear wheels, the center wheels, the cab, the front wheels, all (16) too slowly by. Straight ahead you continue, (17) to cut over sharply would send you into a slip, (18) in front of the vehicle. At last, there is (19) enough, and you creep back over, in front of the truck now, but (20) the sound of its engine still thundering in your ears. 17()
A. meanwhile
B. unless
C. whereas
D. for