读“中国铁路网示意图”回答.
对于△ABC,有如下四个命题: ①若sin2A=sin2B ,则△ABC为等腰三角形,②若sinB=cosA,则△ABC是直角三角形③若sin2A+sin2B<sin2C,则△ABC是钝角三角形其中正确的命题个数是 ( )
—Who can help me carry the heavy box?
—I think David is _______ to do it. But the door is ______for him to go through.