Resolution = 640*480 pixels
No. of bits per pixel=12
Frame Buffer size = Resolution* No. of bits per pixel
=640*480*12 bits
=(640*480*12) /8 Bytes (1 bit = 1/8 Bytes)
=(640*480*12) / (8 * 1024) Kilo Bytes (1 Bytes = 1/ 2^10 Kilo Bytes)
= 450 KB
450 KB is the answer
So option A is correct