A molecular modelling program compares an alkene, X, with three proposed repeating units for its polymer.
| Molecule or proposed repeating unit | Number of carbon atoms | Number of hydrogen atoms | Bond between the two reacting carbon atoms |
|---|---|---|---|
| X | 4 | 8 | double |
| R | 4 | 8 | single |
| S | 4 | 8 | double |
| T | 4 | 6 | single |
Explain which proposed repeating unit is consistent with addition polymerisation. Your answer should also explain whether a molecule other than the polymer would be produced.