单选题

(C)

If one takes a sample of the element gold and starts breaking it into smaller and smaller and smaller pieces, it seems reasonable that one will eventually (最终) reach a "smallest possible piece" of gold that could not be divided further and still be called gold. This smallest possible unit of gold would be a gold atom. Thus, the atom is the limit of chemical subdivision for an element.
The concept of an atom is an old one, dating back to ancient Greece. Records indicate that around 460 B.C., Democritus, a Greek philosopher, suggested that continued subdivision of matter ultimately would yield small indivisible particles which he called atoms (from the Greek word atomos meaning "uncut or indivisible"). Democritus"s ideas about matter were, however, lost (forgotten) during the Middle Ages, as were the ideas of many other people.
It was not until the beginning of the nineteenth century that the concept of the atom was "rediscovered". John Dalton (1776--1844), an English school teacher, proposed in a series of papers published in the period 1803--1807 that the fundamental building block for all kinds of matter was an atom. Dalton"s proposal had as its basis experimentation that he and other scientists had conducted. This is in marked contrast to the early Greek concept of atoms, which was based solely on philosophical speculation (构想). Because of its experimental basis, Dalton"s idea got wide attention and stimulated new work and thought concerning the ultimate building blocks of matter.
Additional research, carried out by many scientists, has now validated (证明……有效) Dalton"s basic conclusion that the building blocks for all types of matter are atomic in nature. Some of the details of Dalton"s original proposals have had to be modified in the light of recent more sophisticated experiments, but the basic concept of atoms remains.

单选题 The first appearance of the idea that the atom is the limit of chemical subdivision for an element was about ______.

单选题 The most important difference between Dalton"s ideas about the atom and those of Democritus was that ______.

【正确答案】 B

【答案解析】[解析] (见第3段4—6行)
1)原文“Dalton’s proposal…had conducted”指出Dalton关于原子的理论是以他自己及其他科学家们都做过的实验为基础的。其中“had as its basis experimentation that…”中 “had”的宾语“experimentation that…”因其过长而后置。指出“the early Greek concept of atoms”(早期希腊人关于原子的概念)。
2)“based solely on philosophical speculation”意为“仅仅依靠哲学理性推断”。
故B)项为答案。

单选题 According to the passage, which of the following is NOT a characteristic of the atom?

【正确答案】 A

【答案解析】[解析] 本题目要求确定哪个选项不是本文中提到的原子的特征。
B)indivisible：不可分的(见第2段第4行)
C)the smallest particle of an element：元素最小的粒子(见第3段第3行)“the fundamental building block for all kinds of matter”(构成一切物质的最基本的结构块)。
D)forms all types of matter(构成一切物质)，在文章中有两次提到：“for all kinds of matter”和“for all types of matter”。
综上列举，只有A)项invisible看不见的在文章中未涉及，故为答案。