The word “commemorate” means to “recall and show respect for (someone or something).” For example: "A wreath-laying ceremony to commemorate the war dead."
Option B: “Remember” means, “have in or be able to bring to one's mind an awareness of (someone or something from the past).” For example: "I remember the screech of the horn as the car came towards me." This is closest in meaning to the word “commemorate”. Hence this is the correct answer.
Option A: “Boast” means, “talk with excessive pride and self-satisfaction about one's achievements, possessions, or abilities.” For example: "She boasted about her many conquests." This is a completely different meaning. Hence, this option is incorrect.
Option C: “Manipulate” means, “handle or control (a tool, mechanism, information, etc.) in a skillful manner.” For example: "He manipulated the dials of the set." This is a completely different meaning. Hence, this option is incorrect.
Option D: “Harmonise” means, “make consistent or compatible.” For example: "The government had plans to harmonise the railways of Europe." This is a completely different meaning. Hence, this option is incorrect.