下列物质中毒具有缺氧和抑制酶的活力双重中毒机制的是（）

A.氰化物

B.汽油

C.硫化氢

D.棉酚

E.砒霜

（）of this deratting exemption certificate is hereby extended until 4th 0ct.1988 as the vessel is laden with cargo.

A.Validity

B.Valid

C.Validation

D.The coming into force