u＝－100sin（6πt＋10°）V超前i＝5cos（6πt－15°）A的相位差是（）
A、25°
B、95°
C、115°
参考答案：C
Some ______are ______their time to help the old people.
A．volunteer; volunteer
B．volunteers; volunteering
C．volunteering; volunteers
D．volunteers; volunteers
沿河路基防护措施有哪些？
