题目

As is known to us. The year 2016 has one extra day in it ——February 29th.This is because it’s 61 we call“a leap year”.Every four years .the year has 366 days in  62  instead of 365. It is called a leap year because hundred of so ago in England ,the extra day wasn’t   63 （legal）recognized .there is a well-known tradition in the UK  64 （associate）with 29th  February ,introduced many centuries ago .women are allowed to break with tradition and propose （求婚）to their boyfriends on this day .this all started back no the   65 （five）century ,when a famous（2012年高考（上海理））在中,若,则的形状是（　　） A．锐角三角形.           B．直角三角形.        C．钝角三角形.  D．不能确定.