（A） increase in the incidence of malaria caused by increasing mosquito resistance against

　　（B） increase in the incidence of malaria because of increasing resistance of mosquitoes to

　　（C） increasing malaria incidence because of increasing resistance of mosquitoes to

　　（D） incidence of malaria increase caused by increasing mosquito resistance against

　　（E） incidence of malaria increase because of increased mosquito resistance to

　　18.Aging is a property ofJ1animakthat reach a fixed size at maturity， and the variations in life spans among different species are far greater as that among individuals from the same species： a fruit fly is ancient at 40 days， a mouse at 3years， a horse at 30， a man at 100， and some tortoises at 150.

　　（A）among different species are far greater as that among individuals from

　　（B）among different species are far greater than that among individuals from

　　（C）among different species are far greater than those

　　（D）between different species are far more than that between individuals of

　　（E）between different species are greater by far than is that between individuals from

　　19.The herbicide Oryzalin was sti11 being produced in 1979， three years after the wives of workers producing the chemical in Rensselaer， New York， were found to have borne children with heart defects or miscarriages， and none of their pregnancies was normal.

　　（A） to have borne children with heart defects or miscarriages， and none of their pregnancies was

　　（B） to gave had children born with heart defects or miscarriages， and none of the pregnancies was

　　（C） either to have had children with heart defects or miscarriages， without any of their pregnancies being

　　（D） either to have had miscarriages or to have borne children with heart defects； none of the pregnancies was

　　（E） either to have had miscarriages or children born with heart defects， without any of their pregnancies being

　　20. Never before in the history of music have musical superstars been able to command so extraordinary fees of the kind they do today.

　　（A）so extraordinary fees of the kind they do today

　　（B）so extraordinary fees as they are today

　　（C）such extraordinary fees as they do today

　　（D）such extraordinary fees of the kind today's have

　　（E）so extraordinary a fee of the kind they can today

　　21. As it becomes more frequent to have spouses who both work outside the home， companies are beginning to help in finding new employment for the spouses of transferred employees.

　　（A）it becomes more frequent to have spouses who both work out side the home

　　（B）it becomes more frequent to have couples both working outside the home

　　（C）it becomes more common that both husband and wife should be working outside the home

　　（D）it becomes more common for both husband and wife to work outside the home

　　（E）coup1es in which6oth of the spouses working outside the home become more common