什么是闰年？
去年是闰年日历添加了一个额外的一天。 this additional day ensures the synchrony between the calendar year and the seasonal/solar/astronomical year. instead of having the usual 365 days, a leap year has 366 days. this is accounted for in the month of february.
中国是世界上最大的煤炭生产国，它已经举办了过去三个十年中的位置。中国每年产生3.7吨的十亿近煤，约占世界总产量的47％代表。