题目内容：

The Canadian red and white maple leaf (枫叶) flag is officially called the National Flag of Canada. The Canadian flag shows a stylized red maple leaf with 11  points on a white background, with red borders down each side. The Canadian flag is twice as long as it is wide. The white square containing the red maple leaf is the same width as the flag.

The red and the white used in the National Flag of Canada were proclaimed the official colors of Canada in 1921 by King George Ⅴ. Although the maple leaf did not have its official status as a symbol of Canada until the announcement (宣告) of the national flag in 1965, it had historically been used as a Canadian symbol, and was used in 1860 in decorations for the visit of the Prince of Wales to Canada. The 11 points on the maple leaf have no special significance.

In the early days，the Royal Union Flag，or the Union Jack, was still flown in British North America. In 1925 and again in 1946, the Canadian Prime Minister Mackenzie King tried to get a national flag of Canada adopted, but failed. In 1964，Prime Minister Lester Pearson appointed a 15-member, all-party committee to come up with a design for a new flag. The committee was given six weeks to complete its task.

The committee studied 2,000 submitted(提交的) designs as well as 3,900 that had been gathered as a result of the 1946 committee's study. Those designs with a chance of being accepted were given to the full committee for further study.

The suggestion of a red and white single maple leaf design for the Canadian flag came from George Stanley, a professor at the Royal Military College. After a heated discussion, they finally decided on his suggestion.

1.How many colors are there in the National Flag of Canada?

A. One.    B. Two.

C. Three.    D. Four.

2.When did Canada have its own national flag?

A. In 1921.    B. In 1860.

C. In 1964.    D. In 1965.

3.What does the underlined word "they" in the last paragraph refer to?

A. The officials of the government.

B. The professors from the Royal Military College.

C. The members of the 1946 committee.

D. The members of the 1964 committee.

4.The passage is mainly about ________.

A. the designer of the National Flag of Canada

B. the history of the National Flag of Canada

C. the meaning of the National Flag of Canada

D. why the red and white single maple leaf was chosen as the design for the National Flag of Canada