下列命题中，正确的命题是（　　）

某村委会的一名成员提出一个事关村民利益的方案，建议在村里建一个体育活动中心，方便村民锻炼身体。该方案应由

It's a sunny day in the farm today. My aunt has a farm. The farm is very small. There are twelve horses, sixteen cows and fifty hens. My aunt likes tomatoes very much. So she has many tomatoes in the farm. Look! The tomatoes are red. They are very beautiful.

My aunt likes potatoes very much.

—Excuse me, could you tell me ______?

—In about 20 days.

如图所示，在磁感应强度为B的足够宽的匀强磁场中，有一个边长为L的正方形线框，线框平面与磁场垂直，则此时穿过线框的磁通量为____．若线框向右平移，线框中有无感应电流？____．若将线框翻转180°，该过程磁通量的变化量为____．该过程有无感应电流？____．若将线框绕其中一边向外转90°，则此时的磁通量变化为____．该过程中有无感应电流？____．