食物链的起始环节是____，有消费者而没有____．
如图，在平面直角坐标系中，二次函数y=ax2+c（a≠0）的图象过正方形ABOC的三个顶点A、B、C，则ac的值是____．
根据材料内容，选择正确答案。
MOVIE GUIDE THURSDAY
Rush Hour 15:00 23:00
My Life as Mcdull 9:00 13:00
①Action Movie
Do you like Jackie Chan? Rush Hour is another movie of his. It's so exciting. Come and have fun!
②Cartoon
Mcdull is a little pig. He's kind of silly but he's very cute. Do you want to enjoy happiness with him? Be sure to watch it!
Mr. Bean 11:00 19:00
Harry Potter Ⅲ 17:00 21:00
③Comedy
Rowan is a great actor. His movie Mr. Bean is coming. It's very funny. Don't miss it!
④Science Fiction
Harry Potter has been in the wizardry school (魔法学校) for three years. He begins a new life. How is everything going?
造成I岛东、西部自然带地域差异的主要原因是（ ）
在π2，0，-49，0.2.3. ，227，3，0.3030030003，1-2中，无理数有（ ）。
纪念中国人民志愿军抗美援朝出国作战60周年座谈会于2010年10月25日在北京人民大会堂隆重举行。结合所学知识回答下列问题：
