燃烧需具备的条件是可燃物、助燃物、着火源。
参考答案：对
________us calmly together,our captain made an announcement _______ we must save only essential supplies before the ship sank. [ ]
A. Calling ; that
B. To call ; that
C. Calling ; which
D. To call ; which
目前，我国个人信用数据库更新个人信息的频率是( )。
A．实时更新
B．每日更新一次
C．每周更新一次
D．每月更新一次
