When antibiotics were first introduced many years ago, they were highly effective in treating infections caused by bacteria. However, in recent years, antibiotics have become less effectivein treating bacterial infections, most likely due to their overuse and misuse. The best explanation for the decrease in antibiotic effectivenessA.bacteria gained the ability to fight against the effects of the antibiotics from the nutrients in their environment.B.antibiotic-resistant bacteria survived, reproduced, and passed their resistant genes to new bacterial generations.C.killed bacteria release enzymes that give surviving bacteria increased resistance against antibiotics.D.the human immune system transferred antibiotic resistance to the bacteria.