题干

一水平弹簧振子做简谐运动,周期为T

A:若t时刻和t+△t时刻振子运动位移的大小相等,方向相同,则△t一定为T的整数倍

B:若t时刻和t+△t时刻振子运动速度大小相等,方向相反,则△t一定为T/2的整数倍

C:若△t=T,则在t时刻和t+△t时刻振子运动的加速度一定相同

D:若△t=T/2,则在t时刻和t+△t时刻弹簧的长度相同

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C

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    Have you ever noticed how terrible weather seems to drag your spirits down?____But there are various things you can do to keep your spirits up until spring.

    ____

    A snowy, icy, cold, or rainy world can be beautiful and often has sounds and smells of its own. If you're an artist, or photographer, winter provides a great deal of inspiration and different colors to work with. Even if you don't feel that creative, simply watching a winter scene from the comfort of your home can be a pleasant way to relax and enjoy the peace.

    Take part in winter activities.

    ____ If you're a beginner to these snow sports, try learning in areas where you won't be worried about more experienced people crowding you out. Local parks are ideal starting points to encourage you to get out and give new winter sports a go.

    ____

    Winter comes with the shortest days and lowest light of the year. Go out if you can. If you can't, or if you're so far from the equator as to have little or no daylight, use bright lights and perhaps light or white walls.

    Stay active.

    As much as possible, get yourself outside. Take at least a short walk. If the weather does not permit, move around inside. Walk up and down your stairs if you have them____ It also regulates such things as sleep and diet. Move around at least a bit each day.

A. Go out.

B. Brighten up.

C. Find things to enjoy about winter.

D. Enjoy skiing, sledding, or ice-skating.

E. There's nothing you can do about the weather.

F. Making snowmen is a fun activity for both kids and adults.

G. Exercise gets your body temperature up and your blood flowing.