To convert the decimal number 26.85 into its binary equivalent, follow these steps:

1. Convert the integer part (26):
   • Divide the integer part by 2 and record the remainder.
   • Continue dividing the quotient by 2 until the quotient is zero.
   • Write down the remainders in reverse order.

   26 ÷ 2 = 13 remainder 0
   13 ÷ 2 = 6 remainder 1
   6 ÷ 2 = 3 remainder 0
   3 ÷ 2 = 1 remainder 1
   1 ÷ 2 = 0 remainder 1

   Writing in reverse order gives: 11010

2. Convert the fractional part (0.85):
   • Multiply the fractional part by 2.
   • Record the integer part of the result (0 or 1).
   • Use the new fractional part for the next iteration.
   • Repeat until the fractional part becomes zero or until the desired precision is achieved.

   0.85 x 2 = 1.70 → Integer part = 1 (Fractional part = 0.70)
   0.70 x 2 = 1.40 → Integer part = 1 (Fractional part = 0.40)
   0.40 x 2 = 0.80 → Integer part = 0 (Fractional part = 0.80)
   0.80 x 2 = 1.60 → Integer part = 1 (Fractional part = 0.60)
   0.60 x 2 = 1.20 → Integer part = 1 (Fractional part = 0.20)
   0.20 x 2 = 0.40 → Integer part = 0 (Fractional part = 0.40)

   The binary fractional part stops at (0.40)^∞, giving 110110 with desired precision.

Therefore, the binary equivalent of the decimal number 26.85 is 11010.110110.

The correct answer is 11010.110110.