In the United States ............. is the most concentrated is New Orleans.

A log grabber has a long arm ............., which stretches out to pick up logs.

A home computer ............. an opportunity for convenient and efficient work at home.

Eli Whitney's milling machine remained unchanged for a century and a half because ............. was so efficient.

Some of the rainwater from clouds evaporates before ..............

Once an offending allergen has been identified ............. tests, it is possible for the doctor to give specific desensitizing injections.

Sometimes ............. wears people out and is worse than the lack of sleep itself.

Although dissimilar in almost every other respect, birds and insects have both evolved efficient ............. capabilities.

The wheel, ............. has remained important for 4,000 years, is one of mankind's first inventions.

............. children master the basics, advanced development becomes easier.