题目

    Hoverboards are quite convient for people to carry or ride on the busy street, especially in college camps, more and more students choose to ride a hoverboard to class.     So hoverboards(电动滑板）were among the most popular Christmas gifts of 2015. They may have also been most dangerous gifts of 2015.     A true hoverboard looks like a skateboard without wheels. To “hover” means to float in the air without moving much in any direction. The popularity of hoverboards began in the 1980s, with the “Back to the Future” movies. Characters in the second and third f7．看电视节目时，如果附近有汽车或飞机从空中飞过，为什么电视屏幕上会出现成串的不规则雪花点，使电视图象受到干扰？