copying differences to different directory

[js_spamfree-rsync at yahoo.com]

sorry for the confusing subject line.  i couldn't think of a better way to say it.  

i'm wondering if rsync can perform the following action:

Compare contents of Directory A (master) to Directory B and copy any differences from Directory A to Directory C (example below)

Directory A:
foo
bar
biz
nis
sum
tin

Directory B:
foo
biz
nis
sum

Directory C:
(empty prior to rsync operation)
bar
tin
(both bar and tin copied from Directory A)

Any assistance that can be provided will be, of course, very appreciated.

--john