题目内容：

Directions: Read the following passage. Fill in each blank with a proper sentence given in the box. Each sentence can be used only once. Note that there are two more sentences than you need.

New sense discovered in dog noses: the ability to detect heat

Dogs’ noses are amazing. Not only are they up to 100 million times more sensitive than ours, they can sense weak thermal radiation- the body heat of mammalian (哺乳动物的) prey, a new study reveals. The find helps explain how dogs with damaged sight, hearing, or smell can still hunt successfully.

“It’s a fascinating discovery,” says Marc Bekoff, an expert on dog sniffing (嗅探). “It provides yet another window into the sensory worlds of dogs’ highly evolved cold noses.” The ability to sense weak, radiating heat is known in only some animals: black fire beetles, certain snakes, and one species of mammal, the common vampire bat, all of which use it to hunt prey.1. But the tips of dogs’ noses are moist, colder than the surrounding temperature, and richly endowed with nerves-all of which suggests an ability to detect not just smell, but heat.

To test the idea, researchers at Lund University trained three pet dogs to choose between a warm (31°C) and a surrounding-temperature object, each placed 1.6 meters away.2. (Scientists could   only detect the difference by touching the surfaces.) After training, the dogs were tested on their skill in double-blind experiments; all three successfully detected the objects emitting weak thermal radiation.

Next, the researchers scanned the brains of 13 pet dogs of various breeds while presenting the dogs with objects emitting neutral or weak thermal radiation. The left somatosensory cortex in dogs’ brains, was more responsive to the warm thermal stimulus than to the neutral one. The scientists identified a group of 14 voxels (体素) in this region of the dogs’ left brains , but didn’t find any in the right, and none in any part of the dogs’ brains in response to the neutral stimulus.

3. Also, a specific region of their brains is activated by this infrared (relating to a type of light) radiation, the scientists say. They suspect dogs inherited the ability from their ancestor, the gray wolf, who may use it to sniff out warm bodies during a hunt.

“The study is consistent with other research that describes the combined dog nose and brain as a highly complicated platform for processing a broad range of signals,” says Gary Settles, a professor of mechanical engineering at Pennsylvania State University. “The dog nose can distinguish patterns of hot and cold objects at a distance,” he said. “4. That needs further study.”

A.If nothing else, the work suggests the extraordinary skills of the dog.

B.The dogs weren’t able to see or smell the difference between these objects.

C.But dogs’ thermal detection skills may not be useful for long distance hunting.

D.Most mammals have naked, smooth skin on the tips of their noses around the nostrils (鼻孔).

E.Dogs track prey “not by sight or sound or smell, but by some other and subtler sense”.

F.Together, the two experiments show that dogs, like vampire bats, can sense weak hot spots.