Since parent of both Justin and his wife Brittany have blood group ab, this means Justin is homozygous(aa) for blood group a and similarly his his wife Brittany is also homozygous (bb) for blood group b. Therefore, Justin and Brittany's son Theodore will certainly have ab blood group.
The advantage of small cell size is that substances like organic molecules and ions can diffuse easily into the cells whereas wastes can diffuse easily out of the cells.
