the marked price of an item is rs4000 and 10% discount is given to make 20% profit by what percent is the discount to be increased to get only 12%profit​

the answer would most likely be c, because if it's a comical piece of information, it may likely not be true, if it's a site that allows anybody to edit the content, it could mean a five year old is typing the info, and if it's a tv show produced by a celeb, it may have a biased opinion.

electric field is a function of 1/r^2

yes, the force per unit charge for a point charge is inverse square law.

3. dark matter

empty space could also be a simple vacuum