When the retina reflects the beams, what occurs?
A．Patients have trouble seeing.
B．The ability to focus is gone.
C．No correction is needed.
D．The lens bends the light beams.

未分类题The authors attitude towards the Visx machine is that______.A．it is interesting but not very usefulB．he says it's a wonderful invention which could replace eye chartsC．it can be useful but he thinks it's too early to make a switchD．too much time and money have been wasted on it

未分类题Why isnt it important what McKay sees in the machine?A．He doesn't like the machine.B．An eye chart is better.C．It's what the machine sees in him that is important.D．The prototype doesn't work very well.

单项选择题高压设备的划分标准是()。

未分类题Which of the following titles is most appropriate to the text?A．The Failed Search for an Earthquake Prediction SystemB．The Merits of Trying to Predict EarthquakesC．The Debate over Earthquake Prediction SystemsD．The Drawbacks of Earthquake Prediction Systems

未分类题Which of the following best sums up activities within an ecosystem?A．Predator-prey relationships.B．Interactions among all members.C．Human-animal interactions.D．Human relationship with the environment.