# Python, <del>19</del> <del>15</del> 14 bytes

a.py

    00000000  70 72 69 6e 00 28 32 50  69 0a 74 22 41 22        |prin.(2Pi.t"A"|

b.py

    00000000  70 72 69 6e 74 22 42 22  00 64 00 00 02 00        |print"B".d....|

c.py

    00000000  00 00 00 00 74 0a 70 72  69 6e 74 22 43 22        |....t.print"C"|

I came up with this solution when I noticed that python (2.7.6 on Ubuntu 14.04) after seeing a NUL character will ignore the rest of that line.

Shortened by 1 bytes once I realized that the space after print wasn't needed. And shortened by 4 more bytes once I realized that the NUL character also cause the newline to be ignored so I can use it to break lines in the middle of a keyword.