肝脏占位性病变二维超声不能肯定诊断时，最好用的检查方法是（）。
A.多普勒超声
B.三维超声
C.M型超声
D.超声引导穿刺活检
E.内镜超声
参考答案：D
— Happy birthday!
— Thank you! It's the best present I _______ for. [ ]
A. should have wished
B. must have wished
C. may have wished
D. could have wished
变压器差动保护产生不平衡电流的原因有哪几点？
