Please read the following table in Markdown format and then answer the question according to the table. Table cells in one row are seperated by '|', and different rows are seperated by '
'.

Table:
| Line | Colour | Route | Length | Stations |
| --- | --- | --- | --- | --- |
| U 1 | red | Reumannplatz – Leopoldau | 14.6km (9.1mi) | 19.0 |
| U 2 | purple | Karlsplatz – Seestadt | 16.7km (10.4mi) | 20.0 |
| U 3 | orange | Ottakring – Simmering | 13.5km (8.4mi) | 21.0 |
| U 4 | green | Hütteldorf – Heiligenstadt | 16.5km (10.3mi) | 20.0 |
| U 6 | brown | Siebenhirten – Floridsdorf | 17.4km (10.8mi) | 24.0 |
Question:
Which line was green?
Answer:
U 4