托福考试备考题和答案

时间:2018-06-02 托福考试 我要投稿

托福考试备考题和答案

  阅读理解

托福考试备考题和答案

  Bloodhounds are biologically adapted to trailing their prey. The process by whichthe nose recognizes an odor is not fully understood, but there are apparently specificreceptor sites for specific odors. In one explanation, recognition occurs when a scentmolecule fits into its corresponding receptor site, like a key into a lock, causing a(Line5) mechanical or chemical change in the cell. Bloodhounds apparently have denserconcentrations of receptor sites tuned to human scents.

  When a bloodhound trails a human being, what does it actually smell? The humanbody, 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(Line10) 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 thebacteria working on both substances is another matter. One microbiologist estimatesthe resident bacteria population of a clean square centimeter of skin on the humanshoulder at "multiples of a million." As they go about their daily business breaking(Line15) down lipids, or fatty substances, on the skin, these bacteria release volatilesubstances that usually strike the bloodhounds nose as an entire constellation ofdistinctive scents.

  45. What does the passage mainly discuss?

  (A) Why people choose bloodhounds for

  household pets

  (B) How a bloodhounds sense of smell works(C) How humans compensate for an

  underdeveloped sense of smell

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

  46. The author compares a scent molecule with a(A) key

  (B) lock

  (C) cell

  (D) bloodhound

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

  (A) bloodhound

  (B) human being

  (C) smell

  (D) body

  48. 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

  49. 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

  50. Which of the following acts as a stimulus in theproduction of the human scent?

  (A) Sweat

  &n

  bsp;(B) Dead skin cells

  (C) Bacteria

  (D) Fatty substances

  参考答案:BAABDC

【托福考试备考题和答案】相关文章:

1.2017年photoshop试题和答案

2.2017年ps试题和答案

3.小学比例应用题和答案

4.小学应用题和答案

5.托福考试备考攻略

6.新托福考试备考策略

7.2017托福考试该如何备考

8.托福考试备考全攻略