题目

Once there was a piano player in a bar（酒吧）. People came just to hear him play. But one night, a lady asked him to sing a song.“I don’t sing,”said the man.But the lady told the writer, “I’m tired of listening to the piano. I want the player to sing!”The waiter shouted across the room, “Hey, friend! If you want to get paid, sing a song!”So he did. He had never sung in public before. Now he was singing for the very first time! Nobody had ever heard the song Mona Lisa sung so beautifully!He had the talent（天赋）he was sitting on! He may have lived the rest of his life 请回答下列显微镜操作的有关问题： （1）上图是显微镜的目镜、物镜及观察到清晰物象时物镜与玻片间的距离。使用上述物镜和目镜观察洋葱鳞片叶时，为使视野中观察到的细胞数目最多，其目镜和物镜的组合是________，物镜与玻片间的距离应该是图________。 （2）下图为显微镜观察到的两个视野，其中甲为主要观察对象，当由视野①变为视野②时，操作方法是________。 （3）下图为A、B两位同学用显微镜观察人的口腔上皮细胞时的效果图，你认为________同学的观察效果好。另一同学效果欠佳是因为装片中有________，要想不出现这位同学视野中不正常的情况，盖玻片时。