根据短文,完成句子
Howisit?
Theoldman(老人)isalreadysixtyyearsold.Buthehasonlyhadfifteenbirthdays.Howisit?Whenishisbirthday?
Keys:HisbirthdayisonFEbruary29th.Itisaleaptear(闰年)everyfouryears.Sohehashadonlyfifteenbirthdays.
1.Theonlyhad()yearsold.
2.Hehadonlyhad()birthdays
3.Hisbirthdayison()
4.Aleapyearhappens(发生)every()years