Which of the following statements listed below is/are examples of differences between gram-positive and gram- negative cells? a. Penicillin would be effective interesting Gram-positive cells than treating gram-negative cells.

b. Gram-positive bacteria flagellar structure has two less rings than do gram-negative bacteria flagellar structure.

c. Gram-positive cells have a mycolic acid layer in their cell walls that holds in stain, whereas gram-negative cells lack this layer.

d. Gram-positive cells have thicker peptidoglycan layers in their cell walls than do gram-negative cells.