1. The same three letters, in the same order, will complete the partial words below:

_ _ _ DE
_ _ _ ME
_ _ _ RE
_ _ _ SE
_ _ _ ZE

2. The same three letters, in the same order, will complete the partial words below:

_ _ _ AT
_ _ _ ET
_ _ _ GO
_ _ _ OM
_ _ _ VE

Answers:

1. The letters are BLA:

BLADE
BLAME
BLARE
BLASE
BLAZE

2. The letters are CAR:

CARAT
CARET
CARGO
CAROM
CARVE