what makes us cry while chopping the onions?
Since this is not my area of expertise, I searched Google under the key words "what makes us cry while chopping onions" to get these possible sources:
https://www.google.com/search?client=safari&rls=en&q=what+makes+us+cry+while+cutting+onions&ie=UTF-8&oe=UTF-8
In the future, you can find the information you desire more quickly, if you use appropriate key words to do your own search. Also see http://hanlib.sou.edu/searchtools/.
http://www.hackcollege.com/blog/2011/11/23/infographic-get-more-out-of-google.html