Dogs have long been used to find explosives and drugs．Now，a new study shows that man’s best friend can also help to find lung and breast cancer，researchers report in integrative Cancer Therapies．The findings show that trained ordinary household dogs can detect early—stage lung and breast cancers by smelling the breath samples of patients．
Researchers have found that cancer cells send out molecules different from those of healthy ones，and that might be sensed by smell by the highly sensitive dog’s nose．
For the study，five dogs were trained by a professional instructor to respond differently to breath samples of healthy and cancer patients．“The dogs learned to sit or lie down in front of cancer patient samples and to ignore control samples through the method of food reward，” McCulloch explained．
After a period of training，researchers tested the animals’ability to distinguish cancer patients from controls．The animals were given breath samples from 55 patients with lung cancer，3 1 with breast cancer and 83 healthy controls who were not included in the original training period．
McCulloch’s group found that the dogs were able to correctly distinguish the breath samples of cancer patients from those of the control subjects in about 90 percent of the cases．The dogs were also able to detecting early-stage lung and breast cancers．
“These results show that there is hope for early detection，”McCulloch said．The re-searches are planning to conduct further studies on the breath composition of cancer patients to possibly design an electronic device that can do the dogs’job．“A dog’s nose is so powerful it can detect odors（气味）10 000 to 100 000 times better than a human nose can．I hope people will be interested in doing this research，”McCulloch added，“It shows that there is definitely something out there．”
65．McCulloch and his group used in their research．
A．10 dogs and 55 people B．5 dogs and 86 people
C．10 dogs and 83 people D．5 dogs and 169 people
66．The underlined work “distinguish” means
A．to make somebody feel better B．to recognize differences of
C．to remember somebody forever D．to discomfort somebody
67．We can infer from the passage that ．
A．dogs can smell signs of other cancers except the above two kinds
B．the final goal of the researchers is to design an electronic dog to detect cancer
C．dogs can detect odors 10 000 to 100 000 times better than humans can
D．dogs will soon be widely used to smell signs of cancers in hospitals
68．Which of the following would be the best title？
A．Special Noses of Dogs B．Dogs and Cancer
C．Dogs Smell Signs of Cancer D．McCulloch’S New Discovery
，则实际功率与额定功率的比值为___________。（用电器电阻不变）