1. a couple of 两三个，几个
Although he thought of the key idea in 1951, the first maser was not completed until a couple of years later.
2. account for 解释
Variations of clay composition and the temperatures at which they are fired account for the differences in texture and appearance.
3. adapt to 使适应于
They have been able to adapt to ecological changes.
4, adorn with sth 用…装饰
Some pots were adorned with incised or stamped decorations.
5.appeal to 吸引
Publishing literature consisting of exciting stories that would appeal to both children and adults
6.apply to 适用于
Ethological theory began to be applied to research on children in the 1960’s.
7.at best 充其量，最多
Hunting is at best a precarious way of procuring food, even when the diet is supplemented with seeds and fruits.
8.at intervals 相隔一定距离
However, at intervals of 10 to 100 years, these glaciers move forward up to 100 times faster than usual.
9.at the expense of sth 在损害…的情况下
A multitude of microorganisms make their livings directly at the expense of other creatures.
10.at the height of sth 在…最鼎盛时期
The violin had reached the height of its popularity by the middle of the eighteenth century.
11.back and forth 来回地
They then spiral back and forth between the Earth's magnetic poles very rapidly.
12.be absent from 缺席，不在
Lacking the right to vote and absent from the seats of power, women line were not considered an important force in history.
13.be capable of 能…的
Many animals are capable of using objects in the natural environment as rudimentary tools.
14. be characterized by 以…为特征
The nervous system of vertebrates is characterized by a hollow, dorsal nerve cord that ends in the head region as an enlargement, the brain.
15.be composed of 由…组成
Ocean life is primarily composed of plants.
16.be concerned with 与某事物有关
Ethnology is concerned with the study of adaptive, or survival, value of behavior and its evolutionary history.
17.be distinct from 与…不同
Jupiter and the other giant planets are of a low-density type quite distinct from the terrestrial planets
18.be essential to 对…不可缺少
Public performance is essential to verbal art.
19.be exposed to 使接触，使遭受
Body contact reduces the surface area exposed to the cold air.
20.be far from 离…很远，根本不是
But far from being random, molt is controlled by strong evolutionary forces that have established an optimal time and duration.
21. be hostile to 极不友好的，极厌恶的
Ocean bottom is a hostile environment to humans
22.be regarded as 被认为是
Humanity's primal efforts to systematize the concepts of size, shapes, and number are usually regarded as the earliest mathematics.
23.be related to 与…有关的，相联系的
Why is dancing closely related to popular music in the United States?
24. be responsible for 对…负责
In fact, nuclear reactions that convert hydrogen to helium are responsible for most of the energy that stars produce.