Hi raju1212.
Learning to see the key differences between the infamous "last two choices" in CR questions is a major part of mastering CR.
One thing you can do to get better at choosing between the last two choices is to understand that they are not really "close." What's actually going on is that one choice is correct and the other one only SEEMS to be close to correct. In other words, the hardest incorrect choice to eliminate is one that is written to appear to do what we need even though it doesn't do that at all.
For instance, in a Weaken question, the correct answer will truly cast doubt on the conclusion, and then there will also be a choice that seems to cast doubt on the conclusion but really does something else, such as cast doubt on a related but different conclusion, or bring up a point that seems to wreck the argument but doesn't really make any difference.
Also, to master CR, you can spend more time on each practice question. If you aren't sure which choice is correct, don't just go with your gut or what seems best. Stick with the question until you have figured out what's going on with the choices and are virtually certain you have found the correct answer.
For some more insights into how to master CR, see this video.
https://www.youtube.com/watch?v=IVKp3TvCWxIAlso, you can get from the following post some more tips on how to practice verbal for best results.
Three Key Practice Tips for Mastering GMAT Verbal