user: Question: What is the second stage that has the third phase of 20kN?
Columns: ['Parameter', '1st stage', '2nd stage', '3rd stage', '4th stage']
Types: ['text', 'text', 'text', 'text', 'text']
Sample row: ['Gross mass', '54,431kg', '462kg', '126kg', '42kg']
SQL:

assistant: SELECT "2nd stage" FROM "Table" WHERE "3rd stage" = '20kN';