The words in each set have a common connection, something that bonds all three of them in some way, shared features or characteristics...a manifestation of common attributes.
Can you find a Commonality?
= 1. RUBBER..VULNERABLE..SLAM
2. COPERNICUS..BRAHE..KEPLER
3. MONKEY WRENCH..MASON JAR..MORSE CODE
4. FINE..HOWARD..HOWARD
5. SUNDAY..RABBIT..KIDNEY
6. RIN..SEN..YEN
= 7. NAIL..CAR..GOLF BALL
= 8. REGULAR..PREMIUM..UNLEADED
9. STROMBOLI..CLEO..GEPPETTO
10. GRANATELLI..FITTIPALDI..SULLIVAN