Here we have to find the subnet mask for which both IP addresses belongs to the different network. ie. When we do Bitwise AND of IP addresses and that subnet mask, result should be different network id.
Option a) 143.105.1.113 & 255.255.255.0 = 143.105.1.0 , 143.105.1.91 & 255.255.255.0= 143.105.1.0
Option b) 143.105.1.113 & 255.255.255.128 = 143.105.1.0 , 143.105.1.91 & 255.255.255.128= 143.105.1.0
Option c) 143.105.1.113 & 255.255.255.192 = 143.105.1.64 , 143.105.1.91 & 255.255.255.192= 143.105.1.64
Option d) 143.105.1.113 & 255.255.255.224 = 143.105.1.96 , 143.105.1.91 & 255.255.255.224= 143.105.1.64
So subnet mask 255.255.255.224 should not be chosen, otherwise A and B will be in different network.
Hence Option d) is correct