简述餐饮产品开发与创新的策略。
参考答案：
Anyone who wants to ________ China’s gardens should go to Suzhou, whose gardens are the best examples in the country.
A．preserve
B．recognize
C．appreciate
D．distinguish
已知A与B均为n阶正定矩阵，证明AB是正定矩阵的充分必要条件是AB=BA．
