The same letters, in the same consecutive order, can be inserted into the words below to make new ones. What are the letters and what are the new words?

BET
MET
PET
WET
BOT  ( a computer software robot)
SHOT
SCION

Answers:

The letter are ALL:

BALLET
MALLET
PALLET
WALLET
BALLOT
SHALLOT
SCALLION