Correct option is B
Pitch of stair:
The pitch of the stairs should match with the French theory the labour of moving vertically is about twice that of moving horizontally, if the average human stride is taken as 23 inches.
If the rise and going are measured in inch units, the best pitch of the stairs is that is that inclination which by twicing the rise and adding the going equals 23. When measured in cm units a comfortable slope a achieved when twice rise plus going is equal to 60 approximately.
In general the slope of stair should never exceed 40° and flatter than 25°.
