Evidence Law--May presume and shall presume--Difference between--In the former case the Court has an option to raise the presumption or not, but in the latter case, the Court must necessarily raise the presumption--If in a case the Court has an option to raise the presumption and raises the presumption, the distinction between the two categories of presumptions ceases and the fact is presumed, unless and until it is disproved--Evidence Act, 1872, Section 4.