血液经过体循环后,其变化是( )
A:由动脉血变成静脉血
B:血液中的二氧化碳含量减少
C:由静脉血变成动脉血
D:血液中养料增多
The old man keeps walking around this street. I think he is new here and now he has trouble ____ (find) his way.
通常条件下属于绝缘体的是( )