An old Indian story says that the game of chess （国际象棋) was invented by Sissa Ben, Prim

An old Indian story says that the game of chess (国际象棋) was invented by Sissa Ben, Prime Minister of King Shirham. As soon as the invention was finished he gave it to the king, who was glad and asked him what he would like to have in return. To the king's surprise, what Sissa wanted seemed very little. "Your Majesty, "said the minister, kneeling before the king. "I want nothing but some wheat. Please put a grain of wheat on the first square of the chessboard (棋盘), two on the second, four on the third, eight on the fourth.., and so on, doubling the number for each following square. Give me enough grains to cover the 64 squares of the chessboard."

"You don't ask for much, my honest servant. You might have asked for gold or money," said the king and then ordered a bag of wheat brought to the palace.

But when the counting began, with one grain for the first square, two for the second, four for the third, and so on, the bag was emptied before the 20th square. More bags were brought, but the number of grain needed for the following squares increased so rapidly that the king was not able to keep his promise even with all the crops in the whole India! In fact, he would have needed 8 466 744 073 709 511 615 grains, which would be as much as that they would produce in about 2000 years!

Now tile king found himself deep in debt to his minister. He had either to face the terrible trouble all his life or to cut off Sissa's head, the litter of which, it is said was what he finally chose.

This story tells us ______.

A．how cruel the king was

B．how clever the minister was

C．Sissa was a famous mathematician

D．how the game of chess came into being