无差异曲线是自右向左弯曲的曲线。（）
参考答案：错
解析：掌握无差异曲线的含义、作用和特征。
SQL语句中，______命令短语的功能是修改表中的记录。
A．Washington, Adams arid Jefferson are most famous in the history of the United States.
B．Washington, Adams and Jefferson had many different interests.
C．Washington, Adams and Jefferson returned home after they were retired.
D．Washington, Adams and Jefferson were the first three Presidents.
