图是人体消化系统模式图，请根据图回答下列问题．（内填代号）

Fill in the blanks with the proper forms of given words.

I helped my mother to buy some beef and three____ (potato) for supper today.

"Belt and Road"（一带一路) are the two wings of developing Asia in the____ (twenty-one) century.

Please keep____ (silence) in the concert hall because people are enjoying Lang Lang's piano performance.

Candy ____ (lay) out the tea, fruit and snacks on the table and waited for the visitors.

.With the development of technology, mobile phones are ____ (wide) used these days.

从1～10中每次取两个不同的整数相加，和不小于12的共有____ 种取法．

某小组将调查的生物进行分类：鲫鱼、金鱼、水草、螃蟹、荷花等归为一类，松、柏、月季、鼠、苍蝇等生物归为一类．他们分类的方法为（  ）