ANS:D - that vary in discrete steps in proportion to the values they represent.

Let's see the binary equivalents of numbers 0-9: a)0000 b)0001 c)0010 d)0011 e)0100 f)0101 g)0110 h)0111 i)1000 j)1001. As seen here, every number with 0 in units place is followed by a number with 1. Also, if a 1 is followed by a series of 1's, next number will be bigger by one bit, with leftmost bit being 1 & rest being 0.

Hence, digital representation follows a definite pattern for positive integers. For fractions, the units place digit maybe replaced by the bit to farthest right & similar pattern maybe observed. Regarding negative numbers, sign bits are set & 1's complement method is used to denote the number.

I know this is not a simple & elegant explanation, but option D fits the description.