The point of the test is to see if, looking at the first terminal, you can tell which rule to use (a requirement for LL). Its pretty obvious for B that there are 2 rules that could apply for the terminal a; its also pretty obvious the each rule for C starts with a different terminal. And you can see that the possible first terminals for C (and hence CBB) overlaps for the other rules for A.
Bottom line: looks good (although, if you had stopped at a single terminal for CBB and happened to choose c, you would have come to the wrong conclusion).