Insects trapped in fossilized amber (琥珀)  for tens of millions of years have provided the key to creating a new generation of antibiotic drugs that could start a war against modern diseases. Scientists have isolated the antibiotics from microbes(微生物) found either from these insects or in soil particles trapped with them when they were caught by sticky tree risen up to 130 million years ago.
Present­day antibiotics have nearly all been isolated from microbes that use them as a form of defense against their enemies and competitors. But since the introduction of antibiotics into medicine 50 years ago, an alarming number have become ineffective because many bacteria have developed resistance to the drugs. Research over the past two years has uncovered at least four antibiotics from the microbes and one has been able to kill modern drug­resistant bacteria that can cause potentially deadly diseases in humans.
Raul Cano, who has pioneered the research at the California Polytechnic State University, said the ancient antibiotics had been successful in fighting drug­resistant strains of staphylococcus (葡萄球菌)，a “superbug” that had threatened the health of patients in hospitals across the globe. He now intends to establish whether the antibiotics might have side effects.  “The problem is how toxic they are to other cells and how easy they are to purify”， said Cano.
Cano's findings have been acknowledged as a breakthrough. A biotechnology company, Ambergene, has been set up to develop the antibiotics into drugs. If any ancient microbes are revived (复活)  that resemble present­day disease, they will be destroyed in case they escape and cause new epidemics. Drug companies will be anxious to study the chemical structures of the prehistoric antibiotics to see how they differ from modern drugs. They hope that one ancient molecule could be used as a basis to produce a range of drugs.
However, even the use of ancient antibiotics may not stop the rise of drug­resistant bacteria. Stuart Levy warned that the bacteria would eventually evolve to fight back against the new drugs. “There might also be an enzyme already out there that can degrade it. So the only way to keep the life of that antibiotic going is to use it sensibly and not excessively，” he said.
28. What problem has man faced since the use of antibiotics as medicine according to the passage?
A. Antibiotics are very difficult to purify.     
B. Antibiotics do harm to human health.
C. Antibiotics resemble some disease­causing bacteria.
D. Antibiotics are becoming ineffective in fighting against bacteria.
29. Why are Cano's findings considered as a breakthrough in science?
A. His discoveries will help revive ancient microbes.
B. His discoveries will put an end to the rise of drug­resistant bacteria.
C. The company Ambergene has applied the prehistoric antibiotics to drugs.
D. The prehistoric antibiotics proved more deadly against drug­resistant modern bacteria.
30.According to the last paragraph, what is Stuart Levy's attitude towards the use of ancient antibiotics ?
A. Cautious.       B. Contradictory.       
C. Confident.       D. Critical.
31. Which of the following can be the best title for the passage?
A. Antibiotics－Dangerous or Not?     
B. Biotechnology Revealed Prehistoric Secrets
C. Insect Antibiotics and Bacteria Evolution     
D. Prehistoric Insects Might Help Invent New Drugs
28-31DDAD