Avoid
subpart labels within a figure part; instead, maintain the established sequence of part labels [e.g., use A, B, C, D, E instead of A, B, C (a), C (b), C ©].
If use of
subpart labels is unavoidable, use lowercase letters (a, b, c).
Avoid
subpart labels within a figure part; instead, maintain the established sequence of part labels [e.g., use A, B, C, D, E instead of A, B, C (a), C (b), C (c)-RSB-.