betterextortedinterpretkettlefeatherfetterlettermettlenettedpatentedpestilentpetulantpretextpretestrestartedretortedsettersettledstatuesquestreettesterteethtemplatetentedtestedtreetoptreatedwetter
There are 12 letters in the following, with two pairs of doubles so the answer is 12!/[2!*2!] = 119,750,400
W and X
Multiplication
MF, as in Mother F*****
vacuum and continuum
Between A and D are two letters, between D and E are no letters, between E and H are two letters, and between H and I are no letters. Therefore, there would be two letters between I and the next letter, so it would be L.
"a" & "b".
Mj, ja
appetite, arrivals
balloon coffee
The last two in that collection are s and s. The next two are e and n.