I’M GOING TO HAVE TO TAKE THE DAY OFF WORK. I FEEL QUITE UNDER THE WE...

Câu 42: I’m going to have to take the day off work. I feel quite under the weather today.

A.

fine

B. ill

C.

sad

D.

sick

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 43 to 50.

For 150 years scientists have tried to determine the solar constant, the amount of solar energy that

reaches the Earth. Yet, even in the most cloud-free regions of the planet, the solar constant cannot be

measured precisely. Gas molecules and dust particles in the atmosphere absorb and scatter sunlight and

prevent some wavelengths of the light from ever reaching the ground.

With the advent of satellites, however, scientists have finally been able to measure the Sun's output

without being impeded by the Earth's atmosphere. Solar Max, a satellite from the National Aeronautics

and Space Administration (NASA), has been measuring the Sun's output since February 1980. Although a

malfunction in the satellite's control system limited

its

observation for a few years, the satellite was

repaired in orbit by astronauts from the space shuttle in 1984. Max's observations indicate that the solar

constant is not really constant after all.

The satellite's instruments have detected frequent, small variations in the Sun's energy output,

generally amounting to no more than 0.05 percent of the Sun's mean energy output and lasting from a few

days to a few weeks. Scientists believe these fluctuations coincide with the appearance and disappearance

of large groups of sunspots on the Sun's disk. Sunspots are relatively dark regions on the Sun's surface

that have strong magnetic fields and a temperature about 2,000 degrees Fahrenheit cooler than the rest of

the Sun's surface. Particularly large fluctuations in the solar constant have coincided with sightings of

large sunspot groups. In 1980, for example, Solar Max's instruments registered a 0.3 percent drop in the

solar energy reaching the Earth. At that time a sunspot group covered about 0.6 percent of the solar disk,

an area 20 times larger than the Earth's surface.

Long-term variations in the solar constant are more difficult to determine. Although Solar Max's

data have indicated a slow and steady decline in the Sun's output, some scientists have thought that the

satellite's aging detectors might have become less sensitive over the years, thus falsely indicating a drop

in the solar constant. This possibility

was dismissed, however, by comparing Solar Max's observations

with data from a similar instrument operating on NASA's Nimbus 7 weather satellite since 1978.