Add the Roman numerals: LXIII + XXXVII = ___.

The correct option is B

C

Combining all the letters of the two roman numerals, we get
L XXXX V IIIII
The IIIII can be written as V. The number can now be written as:
L XXXX VV

The value of VV is 10 which itself can be written as X. The number can now be written as:
L XXXXX

The value of XXXXX is 50 which itself can be written as L. Finally the number becomes
LL.

The value of LL is 100 which is nothing but C. Therefore the correct option is C.