题目内容：

OTTAWA — Canada’s western city of Calgary is the world’s best city when it comes to healthy living, local press reported Monday.

According to an international survey by Mercer Human Resource Consulting, a London-based consulting firm, Calgary was put at the top of a list of 144 cities. It scored 121 points, just above Honolulu’s score of 120. Helsinki（赫尔辛基，芬兰首都） and Ottawa followed at 119.5 and 118.5 respectively.

Three other Canadian cities came in the top 20. Montreal and Vancouver tied for ninth and Toronto came in at 18th.

The scores are based on air pollution levels, availability and quality of hospitals and medical supplies, as well as the efficiency of waste removal and sewage systems.

In America, the lowest scoring city was Atlanta, which was ranked 76th. Athens was the lowest scoring city in Western Europe, ranking 120th because of its air pollution. London was ranked 59th.

56. How many Canadian cities are in the top 20?

A. 3.            B. 4.     C. 5.        D. 6.

57. Which of the following is NOT taken into account when the cities were scored?

A. Weather conditions. B. Air quality.  

C. Waste removal.       D. Medical supplies.

58. Among the following cities, which is the lowest scoring one?

A. Atlanta.        B. Athens.       C. London.    D. Helsinki.