骨髓位于____和____内，分为____和____两类。
参考答案：骨髓腔；骨松质网眼；红骨髓；黄骨髓
Jack Chan _____ to Hollywood a few years ago. Now he ______ a famous
movie star.[ ]
A. went; is
B. has been; is
C. is; is
D. was; was
井下空气中一氧化碳浓度较高时，会使人（）。
A、中毒
B、窒息
C、呼吸困难
