For two 8-bit signed integers A and B in 2's complement format, which of the following will cause an overflow when A and B are added?

For two 8-bit signed integers A and B in 2's complement format, which of the following will cause an overflow when A and B are added?

1. a) 0111 1111 and 1111 1110
2. c) 1000 0000 and 0111 0000
3. b) 0111 1111 and 0111 1110
4. d) 1111 1111 and 1111 1111