题干
.
The symbolic one-hour switch-off first _____ in Sydney in 2007 has become an annual global event.
The symbolic one-hour switch-off first _____ in Sydney in 2007 has become an annual global event.
A：to hold
B：being held
C：to be held
D：held
答案(点此获取答案解析）
D
是抛物线
上一动点，则点
的距离与
的距离和的最小值是 （ ）