某机电工程安装公司承包本市某化工厂车间的洁净空调工程安装任务。其洁净空调设计等级为N7级，并安装了高效过滤器。为保证工程质量，机电安装公司在风管制作、系统严密性检验、系统调试等关键工作中采取了相应的措施。空调工程在竣工验收后，进行了综合效能测定。由于测定结果均符合设计要求，得到业主的好评。
洁净空调工程调试包括：单机试运转；试运转合格后，进行带冷(热)源的不少于 ( )h的系统正常联合试运转。系统的调试应在空态或静态下进行，其检测结果应全部符合设计要求。
A．3
B．5
C．6
D．8
参考答案：D
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| There are 3 basic types of rock climbing.Top roping is probably one of the most common types and the climber basically climbs with a partner.Top roping is a style in which a rope,used for the climber's safety,runs from a belayer(保护员)at the foot of a route through one or more carabiners(铁 锁)connected to an anchor system at the top of the route and back down to the climber,usually attaching to the climber by means of a harness.Assuming that the route is bottomtotop,the toprope climber generally will not fall more than a short distance and can thus safely attempt even the most difficult routes. The second type,which is very similar to top roping is called lead climbing.The buddy(同伴)system works the same way,one man on the ground belaying and the other climbing,but this time instead of the rope being at the top of the rock it has to be hooked into clasps(钩子)as the climber climbs up the rock. In both of these types of rock climbing the climbers has the luxury to sit off the rock face and rest on the rope.However,lead climbing requires the climber to hang from the rock face with one hand,grab the rope ,and pull it up to lip it into the clasps,and this can be very hard depending on many different things. The third type of rock climbing is called bouldering.Bouldering is a type of free climbing without any ropes or harnesses.The climber tends to stay much closer to the ground.This is the most demanding of all climbing.The climber must be able to complete the route without taking a rest on the rope.Often, during a bouldering route the climber is required to do a maneuver called dyno(动态动作). Dynos are basically launching yourself off the rock face,and then grabbing at a hold further away from you.This type of maneuver is where mental training plays a major role in climbing. Believe it or not,climbing is said to be about 75% legs and only 25% arms.To climb successfully one must use wonderful technique.One of the major rules of rock climbing is to always have 3 points touching the rock face.Whether it is both feet and one hand,or one foot and both hands,it is much easier to have your weight distributed on 3 points than it is 2.Another important concept to grasp is that your arms in most cases will not do the climbing；they only hold you into the rock face so that your legs are actually pushing you upward.The closer you are to the rock face,the easier it is to climb. Rock Climbing
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