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