[填空题]Although you may not (success)______ in the beginning, you should keep on trying.

[填空题]Although you may not (success)______ in the beginning, you should keep on trying.

[填空题]Although you may not ______ (success) in the beginning, you should still go on trying.

[单项选择]Although you may think that bottled water is an option than tap, two new reports show that the store-bought stuff is actually less regulated than the water you get out of your tap almost for free.
The Food and Drug Administration (FDA．has little authority to regulate bottled brands, according to a U.S. Congressional report released recently.
While municipal water utilities are required to provide public reports for test results, bottle-water makers are not. So although you may pay a pretty penny for bottled water, that doesn’t mean it’s any better than what’s coming out of your tap. In fact, it could be worse and you’d never know it.
The new research is backed by a report from the Environmental Working Group (EWG). The nonprofit organization surveyed the labels and Web sites of nearly 200 popular bottle-water brands and found that less than 2 percent disclosed three facts that can affect safety: the water’s source, purification (净化) methods, and chemical pollutant (污染物质)
A. has safer water source
B. contains more pollutants
C. is actually less regulated
D. is more strictly regulated

[单项选择]

Although a given waveform may contain frequencies over a very broad range, as a practical matter any transmission system will be able to accommodate only a limited band of （1）. This, in turn, limits the data rate that can be carried on the transmission （2）. A square wave has an infinite number of frequency components and hence an infinite （3）. However, the peak amplitude of the kth frequency component, kf, is only l/k, so most of the （4） in this waveform is in the first few frequency components. In general, any digital waveform will have（5） bandwidth. If we attempt to transmit this waveform as a signal over any medium, the transmission system will limit the bandwidth that can be transmitted.

（1）是（）
A. frequencies
B. connections
C. diagrams
D. resources

[单项选择]Although many of us may feel air-conditioners bring relief from hot, humid or polluted outside air, they pose many potential health hazards. Much research has looked at how the movement of air inside a closed environment—such as an office building—can spread disease or expose people in the building to harmful chemicals.
One of the more widely publicized dangers is that of Legionnaire’s disease, which was first recognized in the 1970s. This was found to have affected people in buildings with air-conditioning systems in which warm air pumped out of the system’s cooling towers was somehow sucked back into the air intake (通风口), in most cases due to poor design. The warm air, filled with bacteria, was combined with cooled, conditioned air and was then circulated around various parts of the building. Studies showed that even people outside such buildings were at risk if they walked past air exhaust pipes.
Large air-conditioning systems add water to the air they circulate b
A. relieve people’s worry about the danger caused by the bacteria
B. help people find an effective way to get rid of the bacteria
C. reflect the serious danger brought by the bacteria
D. cause serious disease such as cancers to people