The difference between a pearl and a cultu

问题单项选择题

The difference between a pearl and a cultured pearl is the nature of the ______.

A．color

B．introduction of the irritating impurity

C．coating material

D．irritating impurity

答案

参考答案：B

解析：[分析] 细节题型。文章第二句(A pearl is the response of a marine…a live mollusk．)指出：天然珍珠中的刺激性的杂物是偶然进入体内的(accidentally introduced into its body)；而人工培育的珍珠中的杂物是人为加入的(the intentional insertion)；所以选项B正确。