【托福真题_英语外教一对一培训】栏目更新了TOEFL托福阅读真题答案（54），以下为具体内容：

　　TOEFL托福阅读真题文章：

　　Bloodhounds are biologically adapted to trailing their prey. The process by which the nose recognizes an odor is not fully understood, but there are apparently specific receptor sites for specific odors.

　　In one explanation, recognition occurs when a scent molecule fits into its corresponding receptor site, like a key into a lock, causing a mechanical or chemical change in the cell. Bloodhounds apparently have denser concentrations of receptor sites tuned to human scents.

　　When a bloodhound trails a human being, what does it actually smell? The human body, which consists of about 60 trillion living cells, sheds exposed skin at a rate of 50million cells a day. So even a trail that has been dispersed by breezes may still seem rich to a bloodhound.

　　The body also produces about 31 to 50 ounces of sweat a day.Neither this fluid nor the shed skin cells have much odor by themselves, but the bacteria working on both substances is another matter.

　　One microbiologist estimates the resident bacteria population of a clean square centimeter of skin on the human shoulder at "multiples of a million." As they go about their daily business breaking down lipids, or fatty substances, on the skin, these bacteria release volatile substances that usually strike the bloodhound's nose as an entire constellation of distinctive scents.

　　TOEFL托福阅读真题

　　1. What does the passage mainly discuss?

　　(A) Why people choose bloodhounds forhousehold pets

　　(B) How a bloodhound's sense of smell works

　　(C) How humans compensate for anunderdeveloped sense of smell

　　(D) The way in which bacteria work on skin cellsand body sweat

　　2. The author compares a scent molecule with a

　　(A) key

　　(B) lock

　　(C) cell

　　(D) bloodhound

　　3. In line 7, the word "it" refers to

　　(A) bloodhound

　　(B) human being

　　(C) smell

　　(D) body

　　4. According to the passage, how many cells ofskin does the human body rid itself of every day?

　　(A) 60 trillion

　　(B) 50 million

　　(C) 1 million

　　(D) Between 31 and 50

　　5. In line 10, the word "rich" is used to mean that atrail is

　　(A) paved with precious materials

　　(B) a profitable business to get into

　　(C) a very costly undertaking

　　(D) filled with an abundance of clues

　　6. Which of the following acts as a stimulus in the production of the human scent?

　　(A) Sweat

　　(B) Dead skin cells

　　(C) Bacteria

　　(D) Fatty substances

　　TOEFL托福阅读真题参考答案：

　　BAABDC

　　以上就是TOEFL托福阅读真题答案（54），欢迎大家进入说客英语官网的【托福真题_英语外教一对一培训】栏目，了解更多托福真题、托福考试内容等相关资讯。