Your heart's mitral valve does an awfully big job. Letting blood from the left atrium of the heart
into the left ventricle without losing a drop is one of the toughest task in the circulatory system.
In fact, if the system was suddenly opened at the point, the force of the valve closing would
send blood five feet in the air.
In this passage, the author's purpose is to - ANSWER convince readers of the stress on the mitral
valve
Riding the mail plane is a low-budget way to visit America's largest national park -- Wrangell-St.
Elias -- 13 million acres of scenic beauty. Copper first drew prospectors to this part of Alaska.
From 1911 to 1938, the Kennicott mine produced 200 million tons of it. Now a mecca for
tourist, the town of Kennicott was abandoned to the ghosts when the copper ran out.
According to the passage, which of the following illustrates the correct sequence of events? -
ANSWER copper drew prospectors, copper ran out, town abandoned, tourist attraction
Physicists seek out those features of nature that are simple and universal. The secret of their
success is not so much a matter of finding answers as it is asking the right questions. The trick is
keeping the questions simple and sticking to universal phenomena. Simple questions can be
answered unambiguously by careful observation of repeated experiments and by logical
thinking.
Which of the following questions is most clearly an example of the kind discussed in the
paragraph? - ANSWER How fast do stones of particular size fall?
An allergy is a hypersensitivity to substances that are essentially harmless. For as yet poorly
understood reasons, the immune system malfunctions and marshals up an army of antibodies
to fight these substances. For many allergies, this malfunction causes a large amount of
histamine to flood into the bloodstream. It is overabundance of histamine that causes allergic
symptoms such as headaches, rashes, and sneezing.