A. One of the X's.
B. One of the I's on the denominator
C. One of the I's on the numerator
D. The V.
E. One of the I's on the right hand side of the equation.
Clarifications and restrictions:
No tampering with the equals sign!
For a valid method, the matchstick that is moved has to be shifted to a different position altogether. For example, if you suggest A, the matchstick cannot remain in the numerator.
No Arabic numerals are allowed!
All Roman numerals formed must be conventionally accepted. For example, 4 should be represented as IV and not IIII.
That's about it, good luck solving folks!