The North lighthouse flashes every $$20$$ seconds.  The South lighthouse flashes every $$25$$ seconds.  The two lighthouses have just flashed at the same time.  How many seconds will it be before they next flash at the same time? 
选项为:A:$$500$$  B:$$300$$  C:$$200$$  D:$$100$$  E:$$50$$  请回答其中一个选项.