电焊机各电路对机壳的热态绝缘电阻不得低于()MΩ。
A.0.1
B.0.2
C.0.3
D.0.4
参考答案:C
--- What have you learned from your experience in Japan?
--- Well, meeting people from another culture ___ be very difficult.
A.must
B.can
C.should
D.shall
下列哪项的细胞不能产生胶原蛋白?()
A.成纤维细胞
B.成骨细胞
C.软骨细胞
D.某些平滑肌细胞和上皮细胞
E.神经胶质细胞