O₃，SO₂，NO₂分析仪，其24h零点漂移应符合（）要求。

A.≤10ppb
B.≤5ppb
C.≤4ppb
D.≤1ppb

A.＜0.5ppb、＜0.5ppb
B.≤0.5ppb、≤0.5ppb
C.＜1ppb、＜1ppb
D.≤1ppb、≤1ppb

A.＜10ppb
B.≤10ppb
C.＜20ppb
D.≤20ppb