According to the passage, laughing gas can be used ______（）

A．A patent holder must publicize the details of his invention when its legal period is over. B．When a patent becomes out of effect, it can be re-patented or extended if necessary. C．It is necessary for an inventor to apply for a patent before he makes his invention public. D．One can get all the details of a patented invention from a library attached to the patent office.

A．The Net allows users to choose their information and to communicate with others. B．Internet communication may be less psychologically satisfying than actual conversation. C．Undeveloped Internet technology causes the drop in psychological health. D．The wider world through the Net makes users less satisfied with their lives.

A．It is very likely to obtain something from a non-profit organization. B．What is not useful for you may be just what others need. C．You may need to create a freecycle organization if you can't find one nearby. D．You have to meet with the giver if you want the thing he offers. 此题为多项选择题。

A．Mr. Johnson's car stood on its boot as it fell down. B．Mr. Johnson could not escape from the door because it was full of sweet jam. C．Mr. Johnson's car accident was partly due to the slippery road. D．Mr. Johnson struggled in the pouring mud as he unscrewed the back seat.

A．City people are less likely to smoke. B．People in rural areas are more likely to smoke. C．Men with higher income tend to smoke. D．Well-educated men with high incomes are generally less likely to smoke.

A．an increasing number of women are entering the workplace. B．women get paid as much as men. C．women's salaries are increasing. D．workplace equality is the key to eliminating poverty.

A．The motor cycles. B．The growing industries. C．The human beings. D．The larger cities.

A．People have become used to crimes now. B．With a TV set some problems can be solved quickly. C．People now like to read books with pictures. D．The adults are less violent than the young.

A．The single biggest food provider was, however, not named after its founder. B．The international cuisine as the Big Mac, a beef hamburger, is provided every chain restaurant in the world. C．Employees in McDonald's have no time to lean. D．The symbol Ronald McDonald, means fun in any language, is said to be the world's most recognized person after Santa Claus.

A．Some coast lines do not have two tides each day. B．Tides are not affected by the shape of coast line. C．The sun has as much effect on tides as does the moon. D．Tides usually rise to the same land day after day.

A.physical distance. B.psychological distance. C.physiological distance. D.philosophical distance.