Transient Lunar Phenomena For many years,

题目：

Transient Lunar Phenomena

For many years, sky watchers have reported seeing mysterious sights known as Transient Lunar Phenomena (TLP) on the surface of the moon. These are of two main types:

fleeting

flashes of light and spreading clouds of mist. Most professional astronomers have tended to dismiss these phenomena as figments of the observers’ imagination or as "observational errors": either optical illusions or problems with the observers’ telescopes. One explanation put forth by professional astronomers blames the flashes on Earth satellites passing in front of the moon. Satellite surfaces can flash like a car’s windshield in sunlight, simulating a lunar flash. It was

this mechanism

that astronomers R. R. Raste and P. Maley used to explain a large lunar flash observed on March 23,1983, and other sightings as well.
One problem with the satellite theory is that TLP were reported long before the advent of artificial satellites. The earliest known account comes from the twelfth-century writer Gervase. On June 18, 1178, in Canterbury, England, Gervase was observing an eclipse of the moon. He was startled by what appeared to be "a flaming torch, that spewed out fire, hot coals, and sparks". Eighteenth-century astronomer Sir William Herschel, discoverer of the planet Uranus, also reported seeing both types of TLP.
He described one TLP as looking like a piece of slowly burning charcoal. In 1830, Andrew Grant, studying the moon from an observatory in Cape Town, South Africa, also observed flashing lights. He told newspaper reporters that he believed the lights came from the sun flashing off clear glass domes that covered cities and forests on the otherwise dead moon. Grant claimed in an interview that he had seen flocks of red and white birds, herds of "diminutive bison", and strange beavers that walked on their hind legs. Not only that, but he claimed even to have seen people with batlike wings who had built towers and pyramids beneath the domes.
In more recent times, a record number of TLP were monitored from 1968 to 1972, during the Apollo missions to the moon. This fact is hardly surprising given that more telescopes were probably trained on the moon during these four years than had been in the entire 270-year history of telescopic observation preceding that time. Though many sightings were dubious, some were highly plausible because they were made by independent observers at different locations. Another notable TLP observation, and the only one confirmed by photographic evidence, took place on April 23, 1994. When over a hundred amateur astronomers reported seeing a dark red cloud spreading across a portion of the Aristarchus crater, astronomer Bonnie Buratti of the Jet Propulsion Laboratory decided to investigate. She got access to photographs of the moon taken by the U.S. lunar mapping satellite Clementine, and indeed, these images confirmed the presence of a reddish cloud obscuring part of the crater.
Even those who believe in TLP cannot agree why the moon sporadically flashes and forms clouds, but many theories have been proposed. Another possibility is that, in some places on the moon, there are chemicals that glow when they are exposed to bursts of radiation from the sun during solar flares.
There is, in fact, some evidence that TLP are observed more frequently during episodes of solar activity. After Project Apollo astronauts brought lunar rocks back to the earth, scientists determined that there are flammable gases inside some moon rocks. Perhaps these rocks crack open and are then ignited by a

stray

spark, causing the flash. However, what causes these rocks to split open
One possibility is "thermal cracking". A rock heats up in the intense sunlight.
Suddenly, when the sun sets, the temperature drops, and the stone cracks. The rocks might also be shattered by "moonquakes", seismic activity on the moon, or by meteors. Scientist R. Zito believes the flashes come not from gas trapped inside the rocks but from the crystals of the rocks themselves. If someone chews a sugar cube in a dark room, sparks appear to come from the person’s mouth as the sugar crystals are crushed. Zito believes that this "sugar cube effect" occurs when meteors smash into lunar rocks, crushing the crystals.
And what about the billowing clouds

The most commonly held belief today is that they are caused by pockets of gas trapped beneath the lunar surface.

The clouds may be caused by the rapid escape of these gases, which kicks up clouds of dust.

The pockets of gas may be freed by moonquakes or the pockets may be punctured by meteors.

The true cause of TLP--if indeed they do exist--is still an unsolved mystery, however, and will probably remain that way at least until humans return to the moon.

Why does the author mention the writer Gervase in paragraph 2 ______

A. To weaken the satellite theory of Raste and Maley.
B. To document the earliest sighting of a lunar eclipse by a scientist.
C. To support the ideas of Herschel and Grant.
D. To provide an early theory about the causes of TLP.