Which one of the following is decimal equivalent of $8$-bit two's complement number $11010011$?

Given $8$-bit two's complement number is:

$11010011$

Since the leftmost bit is $1$, the number is negative.

To find its magnitude, take two's complement.

First, invert all bits:

$11010011\to 00101100$

Now add $1$:

$00101100+1=00101101$

Now convert $00101101$ to decimal:

$00101101=32+8+4+1$

$=45$

Since the original number was negative, the decimal equivalent is:

$-45$