If you work under a car when repairing it, you often get very （ ） .

A.waxy B.slippery C.sticky D.greasy

Students who don’t work hard will face（ ）prospects in the future.

The prisoner（ ）a means of escape from prison.

What you say now is not（ ） with what you said last week.

Saving money regularly during one’s working years will help to（ ）one’s old age from want.

After hydrogen, helium is the second most abundant element in the universe. But how do astronomers know that? It might seem that the philosopher Auguste Comte was on solid ground when he stated in 1844 that, because of the remoteness of the stars, we could never know their chemical composition. Yet only a few years later chemists discovered that under the proper circumstances every element emits a certain combination of colors of light that can identify it, just as your fingerprints can identify you. By analyzing the light coming from stars, astronomers have been able to identify the different chemical elements in the stars and in cosmic space, as well as their relative quantities. It is an interesting historical note that helium was actually found on the sun, in 1868, before it was found on earth, in the 1890s. (The name helium comes from the Greek world hellos, meaning “sun”)The central principle of chemistry is that all matter is composed of atoms. These atoms emit the colors of light that characterize each element. Each atom consists of a nucleus, or positively charged core, and around this nucleus are electrons, which are negatively charged particles. The characteristic light emitted by an atom gives us information about the arrangement of electrons about the atomic nucleus. This arrangement determines the chemical properties of the atom.The atomic number of an element is the number of protons in the nucleus of one of its atoms. The atomic number is a fundamental property, because it also equals the number of electrons around the nucleus in the normal (electrically neutral) atom, and these electrons determine the atom’s chemical properties. The periodic table of the elements (that is, their arrangement into the rows and columns based on their chemical and physical properties) is a result of the way the electrons are arranged in the atoms, and this arrangement or structure depends on the number of electrons and thus on the atomic structure.1.In this passage, fundamental means（ ）.2.The author’s purpose in this passage is to（ ）.3.Auguste Comte said that we could never know the composition of the stars because they are（ ）.4.According to the passage, a central principle of chemistry is that（ ）.5.The tone of this passage can best be described as（ ）.6.The organizational pattern of the first paragraph of this passage is（ ）.7.The author explains the characteristic pattern of color emitted by each element by comparing this pattern to（ ） .