Britain declared war on Germany as a consequence of Germany's attack on Belgium. Option C is correct.
The German invasion of Belgium was a military campaign which began on 4 August 1914.
Belgium's ports were close to the British coast and German control of Belgium would have been considered as a serious threat to Britain. In the end, Britain refused to ignore the events of 4 August 1914, when Germany attacked France through Belgium. Within hours, Britain declared war on Germany.
By the end of the seventeenth century, the Chesapeake area and the southern colonies, with their enormous rice plantations, developed an economic system wholly dependent on slavery.
