—Before he went on the stage，he took a deep ______ ．
—He was too nervous．
____
动物细胞与植物细胞的区别在于动物细胞没有____ 、____ 、____ 。
的定义域为M，集合N＝｛y｜y＝
，x∈R}，则M∩N＝
