Similar discussion thread: http://www.techtud.com/doubt/what-easiest-way-solve-1-tn-tn4-t3n4

Nicely explained!!

@gateaspirant, Expect it very soon.

Below is the great example on fork(). I hope you have gone through it:

http://www.techtud.com/example/very-good-example-fork

bit explanation will be helpful.

From which test the questions do belong ?

@antonio, Can you please help me solving this ?

@jay_krishna, @digvijay, Please have a look.

as they r in proportion i.e a/b=c/d so ad=bc---------(i)

now solving (a-b)(a-c)/a = a^2-ac-ab+bc/a from eqn (i)

(a-b)(a-c) = a^2-ac-ab+ad

taking a common i.e a(a-c-b+d)/a

cancelling a with 1/a gives a+d-b-c i.e OPTION B