(1) Many people are familiar with service dogs: canines who are trained to help those with certain medical conditions or disabilities. (2) However, people might not be aware that the role of dogs in the medical field is expanding. (3) Evidence is mounting that dogs can use their hypersensitive noses to sniff out infections and other diseases in human patients. (4) Through biomedical scent detection, dogs have great potential to help doctors detect medical problems in an effective and efficient way.

Question

(5) Dogs are known for having an acute sense of smell. (6) Search and rescue dogs were first used in the Alps in the 1800s, with Saint Bernards being the most common choice of breed. (7) Humans have already put dogs’ sense of smell to work detecting everything from bedbugs to explosives. (8) In fact, canines’ ability is not limited to infections: dogs have been able to accurately sniff out various types of cancer too. (9) Remarkably, the dogs seem to be able to acquire this skill relatively quickly. (10) In one study, regular pet dogs were trained to detect both lung and breast cancer by smelling patients’ breath. (11) After only two or three weeks of training, the dogs gained success rates of between 88 percent and 99 percent.

(12) Relying on dogs for disease detection is admittedly a new practice, and dogs can be unpredictable. (13) Even proponents of biomedical scent detection is concerned that aspects of the health-care environment might distract dogs from their tasks, and some patients may be uncomfortable having direct contact with dogs. (14) However, the existing research suggests that dogs may be better at detecting disease by sniffing small samples taken from patients than by sniffing the patients themselves. (15) The use of samples would also allow doctors and scientists to control a dog’s surroundings to ensure more accurate results. (16) The potential for canines to provide early warnings of medical conditions in a cost-effective and noninvasive way has made dogs a useful ally in human health care.

Question
In sentence 6, the writer wants to provide evidence that supports the claim in the previous sentence. Which choice best accomplishes this goal?
Responses

NO CHANGE
Answer A: NO CHANGE
A

A dog’s nose contains between 220 million and 300 million scent receptors (by comparison, humans possess between 5 million and 10 million).
Answer B: A dog’s nose contains between 220 million and 300 million scent receptors (by comparison, humans possess between 5 million and 10 million).
B

The first dog to detect cancer in its owner drew attention to a certain mole on its owner’s leg until the owner went to a dermatologist for a diagnosis.
Answer C: The first dog to detect cancer in its owner drew attention to a certain mole on its owner’s leg until the owner went to a dermatologist for a diagnosis.
C

DNA evidence has proved that dogs were domesticated by humans 11,000 years ago, before any other animal.

Answer 1

The best choice to support the claim in the previous sentence (sentence 5), which discusses the acute sense of smell that dogs possess, is:

Answer B: A dog’s nose contains between 220 million and 300 million scent receptors (by comparison, humans possess between 5 million and 10 million).

This choice directly provides evidence that highlights the superior olfactory capabilities of dogs compared to humans, reinforcing the point made in sentence 5 about their acute sense of smell.