37 + 63 = 100
on interchanging the digits of 63 we get 36
36 + 64 = 100
on interchanging the digits of 64 we get 46
46 + 54 = 100
on interchanging the digits of 54 we get 45
45 + 55 = 100
on interchanging the digits of 55 we get 55
Next one is 55,
option 6)