前纵隔常见的肿瘤是（）。
A.淋巴瘤
B.胸腺瘤
C.畸胎瘤
D.神经源性肿瘤
E.支气管囊肿
参考答案：A, B
Especially in adverse weather,risk of collision with an offshore supply vessel increase when the vessel is moored to what side of the unit?（）.
A.Upwind
B.Downwind
C.Crosswind
D.Downcurrent
离心泵的启动操作步骤是怎样的？
