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Exercise 4

Some of the sentences in the following passage are incomplete. From the choices provided, select the word or word group that best completes each sentence.

If you have ever played with two bar magnets, you probably discovered that the ends with opposite charges attract one another. A compass (1) __________ under this basic scientific principle. The needle of a compass is actually a tiny, lightweight magnet. This magnet (2) __________ to the Earth's magnetic field. Like a bar magnet, the Earth has two oppositely charged poles. The south end of the compass needle is therefore attracted to the Earth's North Pole. This is why a compass needle always points due north. A compass is a very useful device, often providing lost travelers with the (3) __________ route home. You may find that you can read a map (4) __________ with a compass in hand.

1. A compass __________ under this basic scientific principle.

 
operate
operates
will operate
has operated
 

2. This magnet __________ to the Earth's magnetic field.
 
will be attracted
was attracted
is attracted
had been attracted
 

3. A compass is a very useful device, often providing lost travelers with the __________ route home.
 
quicker
quickest
most quick
most quickest
 

4. You may find that you can read a map __________ with a compass in hand.
 
clear
most clear
most clearly
clearliest