What do the following phrases have in common? 

1. BACK DATE

2. DOWN PLAY

3. SPACE TIME 

4. CROSS CHECK 

 

Answer:

 

Both words in each phrase can be preceded by DOUBLE to make a common phrase:

 

1. DOUBLE BACK - DOUBLE DATE

2. DOUBLE DOWN - DOUBLE PLAY

3. DOUBLE SPACE - DOUBLE TIME

4. DOUBLE CROSS - DOUBLE CHECK