问题
单项选择题
The scientists found what the isolated roots need is ______
A．quite natural
B．sugar, minerals and vitamins
C．some rare vitamins
D．organic nitrogen compounds
答案
参考答案：B
解析：[分析] 细节题型。 见第一段第三句：They required sugar and the usual minerals and vitamins．所以选项B是答案。