Passage 4There are two major parties in Britain today, the Conservative Party and the Labour Party, which have been in power by turns since 1945.The two—party system of Britain was formed in the course of the development of the capitalist state and the political parties. In order to strengthen the state machine, the British bourgeosie have let it come into being and exist in one form or another form since the 17th century. P.S.Tregidgo once said:“ The more parties there are, the less likely it is that any one of them will be strong enough in Parliament to outvote all the others; but when there are only two, one of them is sure to have a majorityof seats.This helps to ensure a strong and stable government.” This may be the reason why the British have the two party system.The division into two parties grew out the establishment of a Protestant Church of England in the 16th century. Because of a purely religious difference of opinion, the Puritans were separated from the broad body of the Anglican Church. The non Puritan Anglicans were on the side of the King and Church, and their supporters were called by their opponents “Tories.” The Puritans were for Parliament and trade, and their supporters were called by the “Tories” “Whigs”. The Tories and the Whigs were in power by turns for a long time. In 1833, the Tory party split into two and its name was changed to Conservative. In the 1860s the Whigs became Liberals. From that time on, the Liberals and the Conservatives were in office by turns until 1922. The policies they put into effect were sometimes different, but they were both controlled by the rich.The working class became more and more unwilling to follow the Conservatives and the Liberals.They wanted to have their own party. So the Labour party was formed by the trade unions. After 1922 the Labour Party gradually replaced the Liberal Party to become one of the two major parties in Great Britain.　46.What does “it” stand for in the third line?