位图文件的扩展名是（）。
A.JPG
B.GIF
C.BMP
D.WMF
参考答案：C
羊奶中叶酸含量______，长期仅哺给羊奶易致________。
In ship operations，hoisting and lowering pipe in and out of the drilled hole is the main function of the（）.
A.swivel
B.cathead spool
C.drawworks
D.stand pipe
