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 (中心部分). 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 (首位的) 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 (海军的) base in Kingston. It remains in use today primarily for pleasure boating, with most of its original structures still exsiting. The locks on the system open for navigation (通航) in mid-May and close in mid-October.
What does underlined word “iteration” probably mean in the 2nd paragraph?

A．copy

B．repair

C．design

D．picture

If you pay a visit to the core of Downtown Ottawa, you can see ______.

A．a large number of tall towers

B．a lot of apartments and hotels

C．the older single family homes and townhouses

D．head offices of Ottawa’s high tech industry

The main collections in the National Gallery of Canada are ______.

A．paintings and drawings

B．works of art by Canadian artists

C．sculpture and photographs

D．works by American and European artists

What can we know about the Rideau Canal from the passage?

A．The original structures remain unchanged.

B．People can only go boating from May to October.

C．It was originally for the military purpose.

D．It is the oldest canal system in North America.