scject~~
1. Penicillin had been a very effective antibiotic in killing bacteria before. It is now much less effective because
A. resistant strains of bacteria have evolved.
B. penicillin is now produced by a different method.
C. the human body has become less sensitive to penicillin.
D. uncontrolled intake of penicillin affects the immune system of the human body.
2. Which of the following methods of food preservation does not require heating?
A. pasteurization
B. canning
C. salting
D. smoking
3. The first antibiotic discovered by scientists was secreted by:
A. a virus.
B. bacteria.
C. a yeast.
D. a mould.
