(B) III only.
I --> May or may not be true. Take 377 + 855 = 1232. Not true.
II --> May or may not be true. Same eg as above.
III-> Given x<y and x+y = 4-digit integer, let the numbers be of the form
a7b --> x
c5d --> y
f = a+c+1 >= 10
=> a+c > = 9
since x <y, a <= c Hence the least value that "c" can have is 5.
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