[单项选择]Jerome wrote each of the integers 1 through 20, inclusive, on a separate index card. He placed the cards in a box, then drew cards one at a time randomly from the box, without returning the cards he had already drawn to the box. In order to ensure that the sum of all the cards he drew was even, how many cards did Jerome have to draw ？（）
A. 19
B. 12
C. 11
D. 10
E. 3

[单项选择]Jerome wrote each of the integers 1 through 20, inclusive, on a separate index card. He placed the cards in a box, then drew cards one at a time randomly from the box, without returning the cards he had already drawn to the box. In order to ensure that the sum of all the cards he drew was even, how many cards did Jerome have to draw
A. 19
B. 12
C. 11
D. 10
E. (E) 3

[填空题]If r and s are positive integers,each greater than 1,and if 11(s-1)=13(r-1),what is the least possible value of r+s ？（）

[单项选择]If ω, x, y, and z are non-negative integers, each less than 3, and ω(3³)+x(3²)+y(3)+z=34，thenω+z=（）。
A. 0
B. 1
C. 2
D. 3
E. 4

[填空题]

Sharing Economic Losses Through Insurance
Each minute of the day or night, everyone faces a possible financial loss. Savings provide one way to take care of financial losses. But savings are not the answer to large losses. The best way to guard against large financial losses is through insurance.
The purpose of insurance is to provide protection against financial losses at a reasonable cost. This is possible only when the cost of insurance is shared by many people who face a similar risk. But not all of them are likely to have actual losses at the same time.
You Buy Insurance from Insurance Companies
Almost 4,800 companies in the United States are in the business of providing insurance protection. These businesses are called insurance companies. Because most insurance companies operate on a large scale, they provide a way for large numbers of people to share their losses.
Many Kinds of Risks Can Be Insured
Insurance can prov