1. What do the following words have in common?

IF
VICE
VILE
RATED

2. What do the following words have in common?

CUR
JAM
LAM
PLUM
SUPER

HINTS:
1. Each word can be preceded by the same three letters.
2. The same single letter, placed in the same position, will change each word to a new one.

Answers:

1. Each word can be preceded by SER to make new words.

SERIF/SERVICE/SERVILE/SERRATED

2. The letter B can be added to the end of each word to create new words.

CURB/JAMB/LAMB/PLUMB/SUPERB