The average cost of a long-distance call in the USA in 1985 was 50 cents per minute, and the average cost of a long-distance call in the USA in 2008 was 5 cents per minute. Find the approximate percent decrease in the cost per minute of a long- distance call. (adapted from 2007 AMC 8, Question \#6) 
选项为:A:$$30$$  B:$$40$$  C:$$50$$  D:$$80$$  E:$$90$$  请回答其中一个选项.