People with no family history of cancer are unlikely to develop cancer.（）

单项选择题Which is NOT a possible sign of panic disorder（）

A．A fast heartbeat
B．Sweaty hands
C．Difficulty breathing
D．A joyful feeling

单项选择题Since 1955, life expectancy rates in the U. S. have（）

A．moved up and down
B．been declining
C．remained steady
D．been on the rise