— When are you going to fly to Taiwan this summer?— _________ we finish school. It will be a great holiday.
A:Because
B:Since
C:Even though
D:Only if
已知抛物线 y=-x2+1,下列结论:①抛物线开口向上;②抛物线与x轴交于点(-1,0)和点(1,0);③抛物线的对称轴是y轴;④抛物线的顶点坐标是(0,1);⑤抛物线y=-x2+1是由抛物线y=-x2向上平移1个单位得到的.其中正确的个数有
一个正方形木块放在光滑的水平桌面上,下列说法正确的是( )