用偏光仪测试的样品必须是（）宝石。
参考答案：透明——半透明
Mr Green is fond of rock music,___________his wife has no interest in it at all．
A．however
B．while
C．as
D．unless
肾盂肾炎病人常见的致病菌、感染途径和易患因素有哪些？
