题目

 An old lady went out shopping last Sunday. She came to a bank（银行）and saw a car near the door . A man got out of it（下车） and went into the bank . She looked into the car. The keys were in the lock. The old lady took the keys and followed the man into the bank. The man took a gun（枪）out of his pockets and said to the clerk（职员）, “ Give me all the money .” But the old lady didn’t see this. She went to the man and put the keys in his hand and said, “ Young man , you’re foolish . Never leave your keys in your car. Someone’s going to steal（偷）it . 已知x为实数，且|3x-1|+|4x-1|+|5x-1|+…+|17x-1|的值是一个确定的常数，则这个常数是A.5B.10C.15D.75