Ottawa is the capital of Canada. It is the second largest city in Ontario and the fourth largest city in the country.

The Centre Block is the main building on Parliament Hill (国会山). It is also the location of several ceremonial spaces, such as the Hall of Honor and the Memorial Chamber. The present Centre Block is the second iteration of the building，after the first was destroyed by fire in 1916，and it is one of the most recognizable buildings in Canada.

Downtown Ottawa is the commercial and economic centre of the city. Most of the buildings are office towers. While most of Ottawa’s high tech industry is based elsewhere, it has a significant presence in the downtown core. The downtown also contains a number of apartments, hotels, and the older single family homes and townhouses along its edges.

The National Gallery of Canada is one of Canada，s premier art galleries. The Gallery has a large and varied collection of paintings, drawings, sculpture and photographs. Although its focus is on Canadian art, it also holds works by some noted American and European artists.

The Rideau Canal is the oldest continuously operated canal system in North America. At the very beginning，the purpose of the Rideau Canal was military, as it was intended to provide a secure supply and communication route between Montreal and the British naval base in Kingston. It remains in use today primarily for pleasure boating, with most of its original structures remained. The locks on the system open for navigation in mid-May and close in mid-October.
What does "iteration" probably mean in the 2nd paragraph? _____.

A．Repair

B．Design

C．Copy

D．Landmark

In the core of Downtown Ottawa, we could see _____.

A．a large number of tall towers

B．head offices of Ottawa’ s high tech industry

C．a number of apartments and hotels

D．the older single family homes and townhouses

Collections in the National Gallery of Canada are mainly _____.

A．paintings and drawings	B．sculpture and photographs
C．works by Canadian artists	D．artwork by Americans and European

Which of the following is true about the Rideau Canal? _____.

A．It is the oldest canal system in North America

B．It was originally for the military purpose

C．The original structures remain never changed

D．People can only go boating from May to October