The Mayor makes a (solemn) promise to carry out his duties faithfully,and the Lord chief Justice hands the Mayor his swo

The Mayor makes a (solemn) promise to carry out his duties faithfully,and the Lord chief Justice hands the Mayor his sword of office.
A、formal
B、sincere
C、immediate
D、serious
选择正确的选项代替括号内的单词,使得意思不变