A:酸橘入口,分泌唾液
B:人的缩手反射
C:谈虎色变
D:人熟睡时被蚊子叮咬会动一动
Which of the following signs can you often see next to a lake?
下图中有____个圆、____个长方形、____个正方形、____个三角形、____个平行四边形
如图,抛物线y=ax2+bx+c(a≠0)的图象经过点A,B,C,已知点A的坐标为(﹣3,0),点B坐标为(1,0),点C在y轴的正半轴,且∠CAB=30°.