Penicillin (an antibiotic that kills some bacteria) came into widespread use in the 1940s. by the 1990s, several different species of bacteria were already resistant to the effects of penicillin, and it can no longer be used to treat certain diseases. what is the most likely explanation for this?

Which kind of aquatic ecosystem does the photograph most likely show? a. marsh b. swamp c. lake d. river

Which statements correspond to cellular respiration? co2 diffuses passively into the cell. co2 diffuses passively out of the cell. co2 must be pumped out of the cell. o2 diffuses passively when produced inside the cell. o2 diffuses passively when converted to co2. o2 is pumped in and forces co2 out.

Regarding most of the narrator’s story, which word best describes the tone?