List the dates of debates with number of audience bigger than 150
SELECT Date FROM debate WHERE Num_of_Audience  >  150
SELECT Date FROM debate WHERE Num_of_Audience  >  150
[{'Date': 'October 21, 2011'}, {'Date': 'October 27, 2015'}, {'Date': 'January 12, 2017'}, {'Date': 'January 21, 2017'}]