The pitch circle of a cam is

A.The smallest circle drawn to the pitch curve
B.Thesmallest circle drawn to the cam profile from the centre of rotation of a radial cam
C.The circle fitting in the cam profile
D.The circle with centre as the centre of cam axis and radius such that it passes through the point
E.None of the above

Trade will occur when

A.Personnel values are different
B.Middle-men can profit by making trade
C.The exchange leads to more preferred situation for the traders
D.There is enough disparity between the consumption-substitution ratios to cover the costs of trades
E.All of the above