3+4i的平方根是（）
A：3+4i
B：2+i
C：-2-i
D：2+i，或-2-i
--- ______, or we'll be late for the meeting.
--- It's only half past one by my watch. We have enough time left.
Helen is 15 years old, and Joan is 15, too. So Helen is ____ Joan.
