those is plural of that here.. crimes against X and that against Y is wrong.. (that makes the second entity singular) crimes against X and those against Y ( Here those is a relative pronoun standing for crimes against Y)
in A you are using both those and that - redundant and wrong
To decide on right answer you have to ensure parallelism in comparsion:
It is as difficult to ............. as it is to............. is correct and parallel form
you are comparing difficulties of controlling the two kinds of crimes, not the crimes themselves
let me know if any further doubt.
and yes, welcome to the club