下列事件发生的先后顺序排列正确的是(     )

①西安事变     ②红军长征     ③九一八事变     ④日军占领东三省

下列划线词解释正确的一项是（      ）

    China has been drinking tea since the time of Shennong, 5,000 years ago. Britain's relationship with tea is much shorter, but tea enjoys the pride as the UK's national drink. According to the UK Tea Council, British people drink an average of three cups a day or a national total of 165 million cups every day.

    With figures like these, it is no surprise that time spent taking tea affects the working day in Britain. A recent survey found that 24 minutes a day are lost to making, buying and drinking tea and coffee. That is, £400 a year is lost in working hours per employee, or 190 days over a lifetime. So, should employers be worried about this lost working time, or does the tea break make up in other ways?

    One argument is that caffeine(咖啡因) improves mental state: a drink of tea or coffee can make you active and focus on work.

    Professor Rogers of the University of Bristol disagrees. After years of studying caffeine he sees nothing can prove that. “Workers would perform equally well if not drinking it at all,” he says. “But if they're often drinking it and then go without, they'll feel tired and won't perform well.”

    Occupational Psychologist Cooper instead emphasizes the role tea breaks play in sedentary (久坐的) office life, and in building social relationships. “We need to make people more active and see other people. The tea break is one way of doing this,” says Cooper.

    And Professor Rogers also points out the comfort effect of a hot drink: “We warm our hands on them on a cold day; they're comforting and play a big role in our everyday life. Whatever the caffeine's doing, I'd say these 24 minutes aren't wasted.”