no. of chips required= 32k/(256*4)=256
Now we need 8 bits words so we will have to arrange at least 2 chips per row.
Since by constructing memory we will have 127 rows each having 2 chips. So to select a row we need at least log(127) = 7 bits.
So the decoder we need is 7x127 .
Hence (b) is the answer