if `lim_(h->0) [f(a-h)/f(a)]=c` where f(x) is a continuous function such that `f(x)> 0` for all `x in R` and [.] denotes greatest integer function then which of the following statements is always true ? (A) If x=a is a point of local minima then `c in N` (B) if x = a is a point of local maxima then `c in N` (C) If `x=a` is a pioint of local minima then `c in I` (D) If `x= a` is a point of local maximka then `c in I`