外界的平行光线一般认为与眼球相距（）
A.4m以内
B.4m以外
C.5m以内
D.5m以外
E.6m
参考答案：D
点的正投影图是（）
A.点
B.线
C.面
D.圆
E.正方形
A 3-year-old child with Down syndrome is admitted to the pediatric unit with asthma. The child doesn’t enunciate words well and holds onto furniture when he walks. The nurse should ask the mother（）
A. how long the child has been like this.
B. if the child can walk without holding onto furniture.
C. how the child’s condition today differs from his normal condition.
D. if the child always drools.
