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the passage mainly discuss?
(A) The equipment divers use
(B) The effects of pressure on gases in the human body
(C) How to prepare for a deep dive
(D) The symptoms of nitrogen bubbles in the bloodstream.

22.The word "exposed to" in line 8 are closest in meaning to
(A) leaving behind
(B) prepared for
(C) propelled by
(D) subjected to

23.The word "exert" in line 21 is closest in meaning to
(A) cause
(B) permit
(C) need
(D) change

24.The word "diffuses" in line 23 is closest in meaning to
(A) yields
(B) starts
(C) surfaces
(D) travels

25.What happens to nitrogen in body tissues if a diver ascends too quickly.
(A) It forms bubbles
(B) It goes directly to the brain
(C) It is reabsorbed by the lungs.
(D) It has a narcotic effect.

26.The word "They" in line 29 refers to
(A) joints
(B) pains
(C) bubbles
(D) tissues.

27.The word "rupture" in line 36 is closest in meaning to
(A) hurt
(B) shrink
(C) burst
(D) stop

28.It can be inferred from the passage that which of the following presents the greatest danger to a diver?
(A) Pressurized helium
(B) Nitrogen diffusion
(C) Nitrogen bubbles
(D) An air embolism

29.What should a diver do when ascending?
(A) Rise slowly
(B) Breathe faster
(C) Relax completely
(D) Breathe helium.

Question 29-38

Each advance in microscopic technique has provided
scientists with new perspectives on the function of living
organisms and the nature of matter itself. The invention of the
visible-light microscope late in the sixteenth century introduced a
previously unknown realm of single-celled plants and animals.
In the twentieth century, electron microscopes have provided
direct views of viruses and minuscule surface structures. Now
another type of microscope, one that utilize x-rays rather than
light or electrons, offers a different way of examining tiny
details, it should extend human perception still farther into the
natural world.

The dream of building an x-ray microscope dates to
1895, its development, however, was virtually halted in the
1940 s because the development of the electron microscope
was progressing rapidly. During the 1940 s electron micro-
scopes routinely achieved resolution better than that possible
with a visible-light microscope, while the performance of x-ray
microscopes resisted improvement. In recent years, however,
interest in x-ray microscopes has revived, largely because of
advances such as the development of new sources of x-ray
illumination. As a result, the brightness available today is
millions of times that of x-ray tubes, which, for most of the
century, were the only available sources of soft x-rays.

The new x-ray microscopes considerably improve on the
resolution provided by optical microscopes. They can also be
used to map the distribution of certain chemical elements.
Some can form pictures in extremely short times, others hold
the promise of special capabilities such as three dimensional
imaging. Unlike conventional electron microscopy, x-ray
microscopy enables specimens to be kept in air and in water,
which means that biological samples can be studied under
conditions similar to their natural state. The illumination used,
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