Gold numbers of protective colloids A ,B ,C and D are 0.50 , 0.01 , 0,05 and 0.005 respectively , the correct order of their protective powers is

Question

$(a)\;A < C < B < D\qquad(b)\;B < D < A < C\qquad(c)\;D < A < C < B\qquad(d)\;C < B < D < A$