Give you a statement and table with its title in Markdown format, please determine whether the statement is supported or refuted by, or is unrelated to the table. It'a binary classification problem, you should choose the answer between supported and refuted. Table cells in one row are seperated by '|', and different rows are seperated by '
'.

Table:
| fuel gas | upper index kcal / nm 3 | lower index kcal / nm 3 | upper index mj / nm 3 | lower index mj / nm 3 |
| hydrogen | 11528 | 9715 | 48.23 | 40.65 |
| methane | 12735 | 11452 | 53.28 | 47.91 |
| ethane | 16298 | 14931 | 68.19 | 62.47 |
| ethylene | 15253 | 14344 | 63.82 | 60.01 |
| natural gas | 12837 | 11597 | 53.71 | 48.52 |
| propane | 19376 | 17817 | 81.07 | 74.54 |
| propylene | 18413 | 17180 | 77.04 | 71.88 |
| n - butane | 22066 | 20336 | 92.32 | 85.08 |
| iso - butane | 21980 | 20247 | 91.96 | 84.71 |
| butylene - 1 | 21142 | 19728 | 88.46 | 82.54 |
| lpg | 20755 | 19106 | 86.84 | 79.94 |
| acetylene | 14655 | 14141 | 61.32 | 59.16 |
| carbon monoxide | 3060 | 3060 | 12.8 | 12.8 |
Title:
wobbe index
Statement:
n - butane is the fuel gas with the lowest lower index kcal / nm 3
Answer:
refuted