利用二倍体西瓜培育成三倍体无籽西瓜的育种方法属于

    The picture on my desk in my bedroom is my favourite. When I have trouble studying, or I'm worried about an exam, I always have a look at it. It is a picture of my best friends taken three years ago when we were in middle school. Today our lives have gone in different directions, but our friendship has kept us close.

    Every week I get a message from one of them, or a letter with the latest news or vacation photos. 跟其他年份相比，今年我收到了更多的照片。 I often get an email with a joke for the day or words of comfort about some problems in my life. My friends often show up for surprise birthday parties. And one of them even travelled two hours from the other end of a town just to watch my first English speech.