Passage: One party usually has a majority in Parliament, because of the use of the First Past the Post electoral system, which has been conducive in creating the current two party system. The monarch normally asks a person commissioned to form a government simply whether it can survive in the House of Commons, something which majority governments are expected to be able to do. In exceptional circumstances the monarch asks someone to 'form a government' with a parliamentary minority which in the event of no party having a majority requires the formation of a coalition government or 'confidence and supply' arrangement. This option is only ever taken at a time of national emergency, such as war-time. It was given in 1916 to Bonar Law, and when he declined, to David Lloyd George and in 1940 to Winston Churchill. A government is not formed by a vote of the House of Commons, it is a commission from the monarch. The House of Commons gets its first chance to indicate confidence in the new government when it votes on the Speech from the Throne (the legislative programme proposed by the new government).

Question: When is the option taken?
at a time of national emergency