Conversion of an octal number 478 to its binary number is A. 1100112 B. 1001112 C. 1100112 D. 11110112 E. None of the above

The correct answer is A. 1100112.

To convert an octal number to a binary number, you can use the following steps:

1. Divide the octal number by 2, and write down the remainder.
2. Divide the quotient by 2, and write down the remainder.
3. Continue dividing and writing down the remainders until the quotient is 0.
4. Starting from the bottom, read the remainders in reverse order to get the binary number.

For example, to convert the octal number 478 to a binary number, we would do the following:

478 / 2 = 239 with a remainder of 0
239 / 2 = 119 with a remainder of 1
119 / 2 = 59 with a remainder of 1
59 / 2 = 29 with a remainder of 1
29 / 2 = 14

The remainders in reverse order are 1, 1, 1, 1, 0, 1, 1. So the binary number is 1100112.

Option B is incorrect because it is the binary number for the octal number 476. Option C is incorrect because it is the binary number for the octal number 477. Option D is incorrect because it is the binary number for the octal number 479. Option E is incorrect because it is not a valid binary number.