What Is the Difference Between the Sign- Magnitude and 2's-

What is the difference between the sign- magnitude and 2's- complement systems of representing signed binary numbers?

A) In the 2's complement system all numbers, regardless of signs, are entered in the2's- complement preceded by a "1" or "0" to denote sign. In the sign- magnitude method, the magnitude bits represent the true binary value and the bit preceding the MSB represents the sign of the following bits.
B) In the signed- magnitude system all numbers, regardless of their sign, are in straight binary format preceded by a "0" or "1" to denote the sign. In the 2's complement system, the negative numbers are entered in the 2's- complement form preceded by a "1" to acknowledge a negative number whereas positive numbers are entered in straight binary format preceded by a "0" to indicate the sign.
C) In the sign- magnitude system all numbers, regardless of their sign, are in the 2's- complement form preceded by a "0" or "1" to indicate their sign. On the other hand, the 2's- complement system requires the sign- magnitude bits be in straight binary format preceded by a "0" or "1" to denote the proper sign.
D) In the 2's- complement system, all positive numbers are entered in the 2's- complement form preceded by "0" to indicate the sign and all negative numbers are entered in straight binary format preceded by a "1" to indicate the sign. The sign- magnitude system requires that positive and negative numbers be entered in straight binary form preceded by a "0" or "1" to indicate the proper sign.