灾难伤病类型包括()
A.机构损伤所致疾病
B.生物因素所致疾病
C.气体尘埃所致疾病
D.应激性疾病
E.灾难性心理障碍
参考答案:A, B, C, D, E
She often ______ little brother ______ his homework. [ ]
A. helps; doing
B. helps; do
C. help; to do
D. helps; does
金属油罐的阻火器、呼吸阀、量油孔、人孔、透光孔等金属附件必须保持()连接。