The conversion of 10101111001.0111₂ to octal is : 

Concept: 

For binary to octal conversion:

• group of three digits of binary code is converted to octal value.
• octal value lies between 0 to 7.

• Binary value	Octal value
  000	0
  001	1
  010	2
  011	3
  100	4
  101	5
  110	6
  111	7

Calculation: 

In binary number,for making group of three digit, start with left and right of the decimal point that is

10 101  111  001  . 011 1

 we can add zero at the last corners of decimal point to complete the group of three digits.

010 101  111  001  .  011  100  

corresponds to octal value are 

 2       5     7     1    .    3       4

so octal value will be 2571.34

correct option is 3