(Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct word or phrase that best fits each of the numbered blanks from 15 to 19.

Going Inside Black Holes

     One of the strangest phenomena in the universe is the black hole. For years, scientists have studied black holes in an (15) ______ to better understand how they function. Like vacuum cleaners, black holes will suck up anything (16) ______ crosses their path. The incredible sucking power that black holes generate comes from gravity. They can quickly swallow up anything including planets, space debris, and anything else imaginable. Even light cannot escape the (17) ______ of black holes. Since they are able to pull in light, black holes are nearly impossible to see even with high-powered telescopes. (18) ______ scientists are able to detect the presence of black holes in space because of their effect on an observed area. 

     Black holes can originate in a few ways. One type of black holes occurs when a star comes to the end of its lifecycle and it dies in a supernova explosion. They can also occur when the mass of a neutron star becomes so great that it collapses in on itself. Black holes may also occur when several large and dense stars collide with one (19) ______ in space.

Don't egg him on! He gets himself into enough trouble without your encouragement.

In his students’ days, he was as poor as a church ______.

(Mark the letter A, B, C, or D on your answer sheet to indicate the underlined part that needs correction in each of the following questions. 

Which of the following statements can be inferred from the passage?

Mark the letter A, B, C, or D on your answer sheet to indicate the most suitable response to complete each of the following exchanges. 

The author mentions kinglets in paragraph 1 as an example of birds that ________.

Mark the letter A, B, C, or D on your answer sheet to indicate the word(s) OPPOSITE in meaning to the underlined word(s) in each of the following questions.

Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions from 1 to 7. 

     Birds that feed in flocks commonly retire together into roosts. The reasons for roosting communally are not always obvious, but there are some likely benefits. In winter especially, it is important for birds to keep warm at night and conserve precious food reserves. One way to do this is to find a sheltered roost. Solitary roosters shelter in dense vegetation or enter a cavity – horned larks dig holes in the ground and ptarmigan burrow into snow banks - but the effect of sheltering is magnified by several birds huddling together in the roosts, as wrens, swifts, brown creepers, bluebirds, and anis do. Body contact reduces the surface area exposed to the cold air, so the birds keep each other warm. Two kinglets huddling together were found to reduce their heat losses by a quarter, and three together saved a third of their heat. 

     The second possible benefit of communal roosts is that they act as “information centers”. During the day, parties of birds will have spread out to forage over a very large area. When they return in the evening some will have fed well, but others may have found little to eat. Some investigators have observed that when the birds set out again next morning, those birds that did not feed well on the previous day appear to follow those that did. The behavior of common and lesser kestrels may illustrate different feeding behaviors of similar birds with different roosting habits. The common kestrel hunts vertebrate animals in a small, familiar hunting ground, whereas the very similar lesser kestrel feeds on insects over a large area. The common kestrel roosts and hunts alone, but the lesser kestrel roosts and hunts in flocks, possibly so one bird can learn from others where to find insect swarms. 

     Finally, there is safety in numbers at communal roosts since there will always be a few birds awake at any given moment to give the alarm. But this increased protection is partially counteracted by the fact that mass roosts attract predators and are especially vulnerable if they are on the ground. Even those in trees can be attacked by birds of prey. The birds on the edge are at greatest risk since predators find it easier to catch small birds perching at the margins of the roost. 

For some subjects, face-to-face interaction can result ______ better learning outcomes.

Mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the following questions. 

A large number of popular expressions in our language has interesting backgrounds.