What is the sum of each pair of binary integers? a. 10101111 + 11011011 b. 10010111 + 11111111 c. 01110101 + 10101100?

Add digit by digit, from the right, just like any number, except that if it adds to 2, then put a zero and carry one (instead of carrying when it adds to 10 or more).

Example:  < means carry, decimal equivalent for checking
1011+1111

     1     0     1     1         (8+2+1=11)
+   1     1     1     1         (8+4+2+1=15)
---<---<<<
1   1     0     1     0         (16+8+2=26)

Proceeding similarly,
a. 10101111+11011011 = 110001010  (394)
b. 10010111+11111111  = 110010110  (406)
c.  01110101+10101100 = 10010001  (289)

The first option would be correct if it were one half and not one