Answer with Explanation:
These species have different structural composition therefore they possess bacterial resistance towards disinfectants. As Bacillus megaterium belongs to spore producing family therefor it is said that they are most difficult to kill followed by Mycrobacterium bovis having a thick wall with waxy coating. While Pseudomonas aeruginosa is a gram-negative cell and staphylococcus aureus is a gram-positive bacteria.
By following order, you rank their susceptibility to disinfection:
Least Susceptible > Most Susceptible
Bacillus megaterium>Mycrobacterium bovis>Pseudomonas aeruginosa>staphylococcus aureus