user: Question: What channels first aired on 31 December 1990 in the Southern Downs region?
Columns: ['Region served', 'City', 'Channels ( Analog / Digital )', 'First air date', 'ERP (Analog/ Digital)', 'HAAT (Analog/ Digital) 1', 'Transmitter Location']
Types: ['text', 'text', 'text', 'text', 'text', 'text', 'text']
Sample row: ['Cairns 2', 'Cairns', '10 ( VHF ) 3 6 ( VHF )', '7 September 1966', '200 kW 50kW', '1177 m 1190 m', 'Mount Bellenden Ker']
SQL:

assistant: SELECT "Channels ( Analog / Digital )" FROM "Table" WHERE "First air date" = '31 December 1990' AND "Region served" = 'Southern Downs';