witch is the biggest size and SMALLEST?
SIZE A
SIZE C
SIZE D?
c size.
Biggest c smallest a
C-Size is the largest standard size
D-Size is a happy medium between C and A
A-Size is the smallest standard size
and…
E-Sized is Yomega sized bearings, it can be difficult at times to locate bearings this size without paying for Yomega’s name, but it can be done.
I hope this helped 
Just to add on, there is also the Bigyo bearing to consider the biggest bearing, although it is not really used in other yoyos.