This is a sentence improvement question asked in my exam :
It is all but same to me whether I am transferred to Canada or USA.
I have four options to choose from to replace the bold part
A) all or same
B) all the same
C) all one
D) no improvement
If I go by meaning then both options - B and C mean same so considering the structure of the sentence which option is correct here and why ? I am not able to decide between these two options as the meaning given in dictionary is same for both.