单项选择题
A.260mm，280mm B.270mm，280mm C.280mm，270mm D.270mm，260mm
A.＞12MΩ B.＞2MΩ C.＞1MΩ D.＞0.5MΩ
A.≥1.5Mpa B.<0.45Mpa C.≥0.45Mpa D.<1.5Mpa