下列有关固定化酵母细胞制备步骤正确的是（）

Part II Vocabulary and Structure Directions: In this part, there are 10 incomplete sentences. You are required to complete each one by deciding on the most appropriate word or words from the four choices marked A, B, C and D. Children should be allowed to _____ those few years of innocence before they have to learn the truth of the world.A．cherishB．nourishC．flourishD．polish