1. What do the following three-letter words have in common?

JAM
HER
LAM
CUR
PLUM

2. What do the following words have in common?

APE
ONE
ILL
INK

Answers:

1.  Each word can be followed by B to make a new word:

JAMB / HERB / LAMB / CURB / PLUMB

2. Each word can be preceded by DR:

DRAPE  / DRONE / DRILL / DRINK