题目

拓展探究（3分）孟子说“达则兼济天下，穷则独善其身”，请结合选文内容谈谈你对孟子这句话的理解。答：                                                                                                                                                                   下列不具有染色体结构的生物是A.酵母菌B.根霉C.衣藻D.硝化细菌