The boundary between Canada and the United States has been unfortified for over one hundredĐoạn văn19/40Mark the letter A, B, C, or D to indicate the word(s) CLOSEST in meaning to the underlined word(s) in each of the following questions. The boundary between Canada and the United States has been unfortified for over one hundred years.borderbindingrelationshipwaterGiải thíchChọn đáp án A