题目内容：

The Iceberg Was Only Part ofIt

What doomed the Titanic is well known, at least in outline. On a moonless night of April 15, 1912, the ship hit an iceberg in the North Atlantic ,with 1,500 lives lost.

A century later many people presented new theories to explain the real reason for the disaster. Now two new studies argue that rare states of nature played major roles in the disaster.

The first says Earth’s nearness to the Moon and the Sun — a proximity not matched in more than 1,000 years — resulted in record tides that help explain why the Titanic met with so much ice, including the fatal iceberg.

Recently, a team of researchers found an apparent explanation in the heavens. They discovered that Earth had come unusually close to the Sun and Moon that winter, enhancing their gravitational pulls on the ocean and producing record tides. The rare orbits took place between December 1911 and February 1912 — about two months before the disaster came about. The researchers suggest that the high tides refloated masses of icebergs traditionally stuck along the coastlines of Labrador and Newfoundland and sent them adrift into the North Atlantic shipping lanes.

And a second, put forward by a Titanic historian from Britain, contends that the icy waters created ideal conditions for an unusual type of mirage(海市蜃楼) that hid icebergs from lookouts whose duty was to watch carefully for danger ahead and confused a nearby ship as to the liner’s identity, delaying rescue efforts for hours.

Most people know mirages as natural phenomena caused when hot air near the Earth’s surface bends light rays upward. In a desert, the effect prompts lost travelers to mistake patches of blue sky for pools of water. But another kind of mirage occurs when cold air bends light rays downward. In that case, observers can see objects and settings far over the horizon. The images often undergo quick distortions — not unlike the wavy reflections in a funhouse mirror.

Now, scholars of the Titanic are debating these new theories. Some have different opinions on it. Over all, though, many experts are applauding the fresh perspectives. 

1.The underlined word "It" in the title probably refers to _______.

A．the Titanic	B．the cause of the disaster
C．the record tide	D．an unusual mirage

2.According to Theory First, what was the right chain of causes leading to the Titanic’s disaster?

① record tides’ forming and icebergs’ being refloated

② icebergs’ being drifted into the North Atlantic shipping lanes

③ the Earth’s strange closing to the Sun and the Moon

④ increasing of the gravitational force on the ocean

A．①→②→③→④

B．②→③→④→①

C．④→③→②→①

D．③→④→①→②

3.According to Theory Second, the disaster happened to the Titanic mainly because______.

A．the freezing weather made the watcher not be able to watch clear

B．the mirage made the watcher not find icebergs and a nearby ship delay rescuing

C．the mirage on the sea attracted the watcher and made him forget his work

D．the high tides drove the icebergs float so fast that the watcher didn’t respond to them

4.What is the chief function of the sixth paragraph?

A．to explain to the readers the ways of the mirage forming

B．to infer the possibility of the mirage appearing

C．to summarize the various kinds of the mirage

D．to analyze the conditions of the mirage arising

5.This passage is organized generally in the pattern of________.

A．comparison and contrast	B．conclusion and proof
C．time and events	D．definition and classification（分类)