儿童经常食用鱼肝油和猪肝可以预防（ ）。
A：夜盲症和脚气病
B：干眼病和口角炎
C：唇炎和骨软化症
D：夜盲症和佝偻病
若x1、x2是一元二次方程x2+2x-3=0的两个根，则x1+x2的值为（ ）
Today is my birthday. I am a girl. My name is Han Mei. I'm nine years old. I have a birthday party. I have a birthday cake and many gifts. My father and my mother say“Happy birthday!”to me. I'm very happy.
