题干
—We can't be successful ___________ we keep working hard.
—I agree with you.
A：if
B：unless
C：because
D：when
答案(点此获取答案解析）
B
—We can't be successful ___________ we keep working hard.
—I agree with you.
A：if
B：unless
C：because
D：when
的参数方程为
（
为参数），直线
的方程为
，则曲线
的点的
个数为