The same three letters, in the same order, will complete each word below. What are they?

1. C _ _ _

2. D _ _ _

3. G _ _ _

4. P _ _ _

5. T _ _ _

6. D _ _ _ A

7. F _ _ _ E

The letters are RAM:

 

1. CRAM

2. DRAM

3. GRAM

4. PRAM

5. TRAM

6. DRAMA

7. FRAME