Although the Carbon 14 method of dating old objects is not foolproof , it is the best method available at present

People who do not sleep enough tend to become irritable .

One of the greatest breakthroughs for professional women came in 1973 when the field of banking opened up for them.

Solid geometry has enabled astronomers to calculate the positions of the heavenly bodies relative to one another.

Cream of tartar 酒石 , a weak acid, can be added to egg whites to help them foam泡沫 when they are beaten

The Native American interpreter Sacajawea was a valuable member of the Lewis and dark expedition in 1805.

An oversight 遗漏 (miss, overslaugh) in proofreading often results in printed errors.

In the northeastern United States, it rains intermittently 间歇地 throughout the spring.

Insect pests are among the leading causes of crop failure.

Urban renewal programs strive to upgrade areas that are becoming slums.