A:x1=0,x2=4
B:x1=x2=2
C:x1=2,x2=﹣2
D:x1=x2=﹣2
下列有关神经调节和激素调节的叙述中,正确的是( )
In April, the weather in some places in Shanxi was really changeable. People still remember they have _______ four seasons in a week.
在△ABC中,若(a+b+c)(b+c﹣a)=3bc,且sinA=2sinBcosC,试确定三角形的形状.
如图(a)为某班一次地理野外实习的观测点分布图①﹣④为观测点编号,如图(b)为该班某小组在其中一个观测点所作的记录卡片.读图,完成小题
根据如图(b)中记录的信息判断,卡片中“观察编号”应为如图(a)中的( )