Zhang Lin is a middle school student. He is a good boy. Uncle Wu lives next to him. Uncle Wu has no child and can't see anything. He works in the factory (工厂) near Zhang Lin's school. He goes to work at 7:30 in the morning and comes home at 4:30 in the afternoon. Zhang Lin walks to school at 8:00 in the morning and comes home at the same time as Uncle Wu in the afternoon. On weekdays Zhang Lin gets up early to take Uncle Wu to the factory. After school he takes him home. On Sundays Zhang Lin helps Uncle Wu clean the house and do some cooking. Uncle Wu thanks Zhang Lin very much. He says, “Zhang Lin is a good boy. He is like my son.”

若$\sqrt{3-a}$ 在实数范围内有意义，则a的取值范围是(   )

已知一元二次方程$x^2-x-3=0$的较小根为_{$x_1$},则下面对_{$x_1$}的估计正确的是(     ).