颈段前屈角度是
A.45°B.60°C.50°D.80°E.20°
参考答案:A
The first month of the year is ________.[ ]
A. January
B. February
C. March
D. December
国民生产净值又叫( )。
A.GDP
B.GNP
C.NNP
D.PDI