Each of the following sentences contains clues to a set of three words that are spelled the same, except for one letter (each sentence describes a different set). Example: malt, melt, molt.

1) Billy discovered a cylindrical chest buried beneath the knoll.

2) The only evidence found by the detective was some adhesive in the chimney passage.

3) The bashful bovine rested on the small bed.

4) The latest fad was for people to desire the ...

1a) to wriggle 1b) a member of the British gentry 1c) a small forcible stream of liquid

2a) this color is a blend of red and yellow darkened by black
2b) the top of the head
2c) to cover with water

3a) more recent
3b) rubbish
3c) a written communication

4a) free from color
4b) a high-pitched plaintive cry
4c) although

What song lyric does this rebus describe?

Caspar says "Idiots will always enter a burning building."
Melchior says "They will do so, even when no one else will try."
Balthasar says "Not only that, but those dupes will do it quickly."

Which word in Group B can be added to Group A? Why?

Group A: complex, on, rat, stall
Group B: accord, gallop, new, tandem