X线平均波长（λmean）与最短波长（λmin）的关系，正确的是

A:λmean=3.5λmin B:λmean=3.2λmin C:λmean=2.8λmin D:λmean=2.5λmin E:λmean=2.2λmin

X线平均波长（λ）与最短波长(λ)的关系是

A:λ=3λ B:λ=2.5λ C:λ=2λ D:λ=1.5λ E:λ=λ

Mean arterial pressure:

Mean arterial pressure:

The maximum difference between mean time and apparent time is _____．

A:equal to the longitude expressed in time units B:about 1minutes C:the difference between the GHA of mean sun and the first point of Aries D:15°of arc"

What doesOBO mean?

A:Oil Bulk Oil B:Ore Bulk Oil C:Only Bulk Ore D:Only Basic Oil"