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
- 科普版6年级下册 动词过去式汇总
- 食品安全与日常饮食 平时