Predicting the future is difficult. So no one knows what the life _______ like in hundreds of years.

A. will be             B. is               C. was

如图中，金属棒ab 置于水平放置的导轨上向右作切割磁感线运动．请标出流过金属棒ab的电流方向，以及ab棒受安培力的方向．