题目

44．很多实验中必须先制作玻片标本，然后在显微镜下观察。下面的实验步骤错误的是（    ） A．脂肪鉴定：切取花生子叶薄片→染色→去浮色→制片→观察 B．有丝分裂观察：解离根尖→染色→漂洗→制片→观察 C．质壁分离观察：撕取紫色洋葱鳞片叶表皮→制片→观察→滴加蔗糖溶液→观察 D．细胞质流动观察：取黑藻小叶→制片→观察Although he was in poor health, Robert succeeded ______  other more famous engineers failed. A. which           B. that        C. what       D. where