Given the numbers : 161 cm, 0.161 cm, 0.0161 cm. The number of significant figures for the three numbers are

All non zero digits are significant ;   Ex: In  161cm , the number of  S.f = 3                                                                                  In 0.161cm , the  number of  S.f = 3Zeros preceding to first non zero digit are not significant;  ex: In 0.0161cm, the number of  S.f = 3(S.f= significant figures)