已知半径分别为2和3的两个圆有两个交点,则圆心距d的取值范围是______.
∵半径分别为2和3的两个圆有两个交点,
则可知两圆相交;
∵3-2=1,3+2=5,
∴1<d<5.
They ________ have arrived at lunchtime but their flight was delayed. [ ]
A. will
B. can
C. must
D. should
船舶至少()要进行一次消防演习,并且每次间隔日期不等,以避免船员预料到演习时间。
A.一个周
B.一个月
C.三个月