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问题 选择题

我国冬季南北温差大的主要原因是（　　）

①地形的影响②纬度位置的影响③冬季风的影响④海陆位置的影响．

A．①②

B．②③

C．③④

D．①④

答案

纬度位置是影响我国气温分布的重要因素．我国幅员辽阔，南北跨纬度将近50度，冬季太阳直射点在南半球，我国北方的正午太阳高度比南方低，昼短夜长，得到的太阳光热自然比南方要少；加之冬季风频频南下，我国北方首当其冲，寒冷的冬季风加剧了我国北方的严寒，冬季风南下过程中，受到重重山岭的阻挡，势力逐渐减弱，南方受冬季风的影响而降温的程度，远比北方小，所以我国冬季越往北去，气温越低，南北气温相差很大．根据题意．

故选：B．

选择题

如图所示，一轻弹簧左端与物体A相连，右端与物体B相连，开始时，A、B均在粗糙水平面上不动，弹簧处于原长状态。在物体B上作用一水平向右的恒力F，使物体A、B向右运动。在此过程中，下列说法中正确的为 （   ）

A．合外力对物体A所做的功等于物体A的动能增量

B．外力F做的功与摩擦力对物体B做的功之和等于物体B的动能增量

C．外力F做的功及摩擦力对物体A和B做功的代数和等于物体A和B的动能增量及弹簧弹性势能增量之和

D．外力F做的功加上摩擦力对物体B做的功等于物体B的动能增量与弹簧弹性势能增量之和
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单项选择题

Questions 26～30


It was books that first captured my imagination about faraway places. TV travelogues always seemed the poor relation to the classic written accounts, although of course the pictures were rather better. And then there was the issue of authenticity. All those pretentious theatrical types dying of thirst in the desert, as if we didn’t realize there was a camera crew on hand to cater for their every need. These days programme-makers know that the audience is more sophisticated and the presence of the camera is acknowledged. But can a journey with filming equipment ever be anything other than a cleverly constructed fiction
I recently got the chance to find out, when I was asked to present two one-hour programmes for an adventure travel series. The project was the brainchild of the production company Trans-Atlantic Films, which wanted the series presented by writers and adventurers, as well as TV professionals. My sole qualification was as a journalist specialising in "adventure" travel. However, I was thought to have "on-screen" potential.
The first programme was filmed in Costa Rica. Within 24 hours of my arrival, I realized that this was going to be very different from my usual "one man and his laptop" expeditions. For a start, there were five of us—director, cameraman, sound recordist, producer and presenter. And then there was the small matter of ￡100,000 worth of equipment. I soon realized that the director, Peter Macpherson, was a vastly experienced adventure film-maker. In his case, the term "adventure" meant precisely that. "Made a film with X," he would say (normally a famous mountaineer or skier), before describing a death-defying sequence at the top of a glacier in Alaska or hand-gliding off the Angel Falls in Venezuela. Invariably, these reminiscences would end with the words: "Had a great deal of respect for X. Dead now, sadly... "
Part of the brief for the series was to put the presenter in unusual situations and see how he or she coped. One such sequence was the night we spent in the rainforest canopy near the National Park in Guanacaste province. I don’t have a head for heights and would make a poor rock-climber, so my distress is real enough as the camera catches me dangling on a rope some 30 metres up, well short of the canopy platform.
Ironically, it was the presence of the camera, looking down on me from above, that gave me the impetus for the final push to the top. By this time, I’d learnt how "sequences" were cut together and realized that one last effort was required. I had to struggle to stay coherent while the camera swooped within a few millimeters of my face for my reaction In the end, it was a magical experience, hightened all the more by the sounds of the forest—a family of howler monkeys in a nearby tree, amplified through the sound recordist’s headphones.
Learning how to establish a rapport with the camera is vital and it took me a while to think of it as a friend rather than a judge and jury. The most intimidating moments were when Peter strolled up to me, saying that the light would only be right for another 10 minutes, and that he needed a "link" from one sequence to another. The brief was simple. It needed to be 30 seconds long, sum up my feelings, be informative, well-structured and, most important of all, riveting to watch "Ready to go in about five minutes" he would say breezily.

What does the writer say about the last part of the sequence in the National Park ______

A. It taught him a lot about the technical aspects of film-making.
B. He was encouraged to complete it when he looked up at the camera.
C. It changed his whole attitude towards doing dangerous things.
D. He was unable to say anything that made sense at this time.
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