The most common time for tornadoes to occur are in the afternoon or evening on a hot, humid spring day.

• most common

• tornadoes

• are

• hot, humid

John Chapman became famous in America folklore as "Johnny Applessed" after he plants apple trees throughout the northeastern part of the United States.

• famous

• plants

• throughout

• part of

Bats avoid running into objects by ... high-frequency sounds and listening for echoes.

• the emission

• emitted

• emitting

• they emit

Because of his reservations about the issue, ... refused to vote for it.

• who

• and

• which the senator

• the senator

It has been estimated that if we intend to stay above the starvation level, ... the food supply.

• so we will have to double

• and it must double

• which it must be doubled

• we must double

When a country in an early stage of development, investments in fixed capital are vital.

• country in

• investments

• fixed

• are vital

... in the United States declined from twenty million in 1910 to nine million in the 1970's.

• For a number of heroes

• The number of horses

• When the number of heroes

• that the number of heroes

Inasmuch he kept mostly to himself, the author of The Treasure of the Sierra Madre was known as the mysterious B. Treuen

• Inasmuch

• mostly

• to himself

• was

To determine an object's force, the mass and speed of the object must be measure.

• To determine

• mass and

• the

• measure

Automakers Nissa and Ford and several aerospace research facilities in Great Britain are working lately to apply active noise cancellation to entire cars and planes.

• several

• are working

• active noise cancellation

• to entire