A:波斯湾
B:黑海
C:红海
D:阿拉伯海
有下列命题:①面积相等的三角形是全等三角形;②“若xy=0,则|x|+|y|=0”的逆命题;③“若a>b,则a+c>b+c ”的否命题;④“矩形的对角线互相垂直”的逆否命题.其中真命题共有 ( )
如图所示的向日葵图案是用等分圆周画出的,则⊙O与半圆P的半径的比为( )
—Our class will have a party the evening of June 30th. Would you like to come? —Yes, I'd love to, but I'm going to visit my grandparents in Dalian.