课时作业23 Unit 3 Life in the future
Ⅰ.单项填空
1．(2013·长春模拟)Obama，the first black president in American history，________presidency on January 20th,2009.
A．held up B．took up
C．pi cked up D．set up
解析：考查动词短语辩析。句意：奥巴马，美国历史上第一位黑人总统，于2009年1月20日就职。take up从事，开始，take up presidency“开始总统任期”符合句意。hold up举起，支撑，耽搁；pick up拾起，捡起；set up 建立，创立。
答案：B
2．Everything will be all right. We must never stop taking a(n)________attitude towards life.
A．understanding B．opposite
C．relaxed D．optimistic
解析：句意：所有的一切都会好的，我们要始终对生活抱乐观的态度。optimistic意为“乐观的”，符合句意。understanding体谅的；opposite相反的；relaxed放松的。
答案：D
3．Hearing footsteps outside the door the hostess________her conversation to another topic.
A．switched B．exchanged
C．contributed D．put
解析：switch...to把……转移/变换到……；exchange...with和……交换；contribute to...做贡献，促成。
答案：A
4．The foreign guests are deeply impressed by the________flow of bikes in the street.
