In 1931 by _______ Canada was formally declared to be a sovereign nation and became a member of the Commonwealth of Nations.
A、the Peace Treaty of 1919
B、the Statute of Westminster
C、the Meek Lake Accord
D、the Constitutional Act
【正确答案】：B
【题目解析】：1931年，根据威斯敏斯特法令，加拿大正式宣布成为一个主权国家，并成为英联邦的一员。
