患者方某，女性，34岁，遵医嘱行一次性导尿术留取无菌尿标本，下列符合无菌操作原则的是（）

A.打开导尿包后，用手将小药杯置于边角

B.先戴好无菌手套，再铺孔巾

C.导尿管误入 * * ，应拔出后立即重插

D.用物污染后应立即用酒精棉球擦拭

E.留取前段尿液5ml作细菌培养

Many Chinese students think science subjects are ________ foreign languages.[ ]

A. more difficult as

B. less difficult than

C. much difficult than

D. so difficult as