The best title for this passage is （）

单项选择题How do scientists know Motherhood may make women smarter （）

A．Some researchers have told them.
B．Many women say so.
C．They know it by experimenting on rats.
D．They know it through their own experience.

单项选择题The purpose of this passage is to tell people that （）

A．most old people die from accidents at home
B．up to half of home accidents could be prevented
C．falls at home can be avoided by taking some simple measures
D．protection of old people should be the first concern for the public