通常，人们按照地理方位，把亚洲分为东亚、_______亚、_____亚、_____亚、北亚和_____亚6个地区。
东南；南；西；中
—What do you think of the 3-D printer?
—It’s great although it still needs further .
A．arrangement
B．education
C．information
D．development
铝热焊缝距轨枕边不得小于（）。
A.25mm
B.30mm
C.35mm
D.40mm
