TOEFL Structure and Written Expression 7 (Longman PBT)

The planet Mercury __ rotations during every two trips around the Sun.

In prehistoric __ of western Utah was covered by Lake Bonneville.

The helicopter is able to hover in __ powered rotors produce lift even at zero forward speed.

The upper levels of the Sun's atmosphere are of very low __ heats the gases there to very high temperatures.

Lapis lazuli, __ stone, has been valued for ornamental purposes for more than 6,000 years.

Mountaineers __ climb Mount Everest must make reservations to do so, often up to seven years in advance.

Created by the dissolution of limestone, the underground cave system __ Mammoth Cave is noted for its stalactites and stalagmites.

Most slang terms are simply old words additional new meanings.

North Carolina's Outer Banks are a chain of low, narrow islands __ the mainland from the frequent Atlantic storms in the area.

It is at the age of approximately eighteen months __ children begin to make combinations of two or three words.