如图,AB是圆O的直径,点C在圆O上,延长BC到D使BC=CD,过C作圆O的切线交AD于E,若AB=8,DC=4,则DE=( )
A:2
B:2
C:233
D:43
正常健康人的尿液中不可能有的物质是( )
①葡萄糖 ②无机盐 ③血细胞 ④大分子蛋白质.
如图是某人在一次平静呼吸中肺内气压的变化曲线.请分析曲线BC段的变化中,胸廓的前后径和左右径的变化分别是( )
A:Hello,Tom.
B:Hi,Jenny. How do you feel?
A:I feel happy. Look! This is my sister(妹妹).
B:What's her name?
A:Her name is Kate.
B:What colour is her hair?
A:Her hair is black.
B:What colour are her eyes?
A:They are blue.
B:How nice(漂亮的)!
鸦片战争后,中国自然经济开始解体的标志是