题目

已知M2O7x- + 3 S2- + 14 H＋ = 2 M 3＋ + 3S ↓ + 7H2O,则M2O7x-中的M的化合价为( )A. ＋2 B. ＋3 C. ＋4 D. ＋6 答案：【答案】D【解析】该反应是离子反应型的氧化还原反应，可以根据电荷守恒计算，可以得到式子：-x+3×（-2）+14=2×3，x=2，则M2O72-，假设M的化合价为y，则有-2×7+2y=-2，y=-6，所以答案D正确。故选D。　　Cheats have taken large amount of money out of trusting Japanese in 2003 by phoning and pretending to be relatives in trouble, Japanese police said. In what media are calling the“Hi, it's me”trick, victims（受害者）receive calls from cheats who call themselves only as“me”and say they are in great need of money to cover anything from an uninsured traffic accident to an unexpected trouble. Victims think the person on the telephone must be a close relative and often agree to send the money to bank account specified by the cheat straight away. There had been 3 807 reported cases till November 2003, with victims paying out a total of almost 2.3 billion yen ($ 21.1 million), according to police figures. Many of the victims were women over 40, according to domestic newspapers. Police said they were recommending that people check the identity of people asking for money on the telephone. In a more shocking development, some telephone cheats now force money by pretending they have kidnapped a victim's child, with 76 such cases in October alone. (1) Why did the victims send money to the cheats? [　　] A．Because they recognized their close relatives in trouble. B．Because they thought the person on the phone was close relative though they didn't recognized who it was. C．Because the cheats pretended to be their close friends. D．Because the cheats called themselves their close relatives. (2) Who were more easily cheated in the trick? [　　] A．Children.B．Old men. C．Young people.D．Older women. (3) According to the passage, the more worrying tend is ________. [　　] A．there will be more and more cases in Japan B．a larger amount of money will be paid out by victims C．Japanese take no notice of the warning by the police D．cheats pretended they have taken more dangerous actions when they asked for money (4) The best title of this passage might be“________” [　　] A．Hey, I'm in Trouble!B．Hey, Help Me! C．Hey, It's Me! Send Money!D．Hey, I Need Money Badly!