hi, all

I am an asian, and confused with these grammar.

A.I eat more than he does.

B.The priciple could have greater significance than do the particulars.

C.Tiny quantities threaten to warm the atmosphere more rapidly over the next fifty years than carbon dioxide will.

1.In sentence B, is that moveable to put the word "do" after "the particulars"?
If not, how to explain the sentence A that the "does" is placed behind the subject?
or should I replace "do" with "could"?
as the word "will" (in sentence C) makes the verb be omitted.

I am sorry for my bad description and expect to ur assistances.
thx