Why do antibiotics become less effective overtime?

Disinfection of impression materials is usually accomplished by a. sterilization with high heat. b. spray or immersion in a chemical disinfectant. c. sterilization with steam under pressure. d. allowing the impression to sit 24 hours in water until all the organisms die.

Which of these statements are true about scientific theories and hypothesis

Which units ate used to measure both velocity and speed? check all that apply