My fellow-citizens, no people on earth have more cause to be thankful than ours, and this is said reverently, in no spirit of boastfulness in our own strength, but with gratitude to the Giver of Good who has blessed us with the conditions which have enabled us to achieve so large a measure of well-being and of happiness. To us as a people it has been granted to lay the foundations of our national life in a new continent. We are the heirs of the ages, and yet we have had to pay few of the penalties which in old countries are exacted by the dead hand of a bygone civilization. We have not been obliged to fight for our existence against any alien race; and yet our life has called for the vigor and effort without which the manlier and hardier virtues wither away. Under such conditions it would be our own fault if we failed; and the success which we have had in the past, the success which we confidently believe the future will bring, should cause in us no feeling of [vanity], but rather a deep and abiding realization of all which life has offered us; a full acknowledgment of the responsibility which is ours; and a fixed determination to show that under a free government a mighty people can thrive best, alike as regards the things of the body and the things of the soul. Much has been given us, and much will rightfully be expected from us. We have duties to others and duties to ourselves; and we can shirk neither. We have become a great nation, forced by the fact of its greatness into relations with the other nations of the earth, and we must behave as beseems a people with such responsibilities. Toward all other nations, large and small, our attitude must be one of cordial and sincere friendship. We must show not only in our words, but in our deeds, that we are earnestly desirous of securing their good will by acting toward them in a spirit of just and generous recognition of all their rights. But justice and generosity in a nation, as in an individual, count most when shown not by the weak but by the strong. While ever careful to refrain from wrongdoing others, we must be no less insistent that we are not wronged ourselves. We wish peace, but we wish the peace of justice, the peace of righteousness. We wish it because we think it is right and not because we are afraid. No weak nation that acts manfully and justly should ever have cause to fear us, and no strong power should ever be able to single us out as a subject for insolent aggression.
Which word suggests a topic of the speech?
Aggression
Duty
Peace
Realization

The speech talks about a nation's duty towards righteousness and justice, not only when discussing political and public matters, but also personally, as a virtue all people must carry inside themselves. At the beginning of his speech, the speaker conveys a feeling of gratitude for all that was given to his people, when he says "with gratitude to the Giver of Good who has blessed us with the conditions which have enabled us to achieve so large a measure of well-being and of happiness". Then, the speaker calls attention to the fact that "Under such conditions it would be our own fault if we failed", meaning that his people should consider their responsibility any wrong actions they would be driven to take. As free and mighty people, he/she says that "a full acknowledgment of the responsibility which is ours" is necessary. When the speaker states that "We must show not only in our words, but in our deeds", he/she makes it clear that, as consequence of their well-being and success, they have the opportunity and the obligation to be right and just toward other nations. Therefore, the main topic of this speech would be the people's duty towards others, considering their privileged position.

The correct answer couldn't be the first option, "Aggression", because this word is only mentioned in the end, when the speaker says that "no strong power should ever be able to single us out as a subject for insolent aggression", as a result of their actions taken with justice, which takes the reader one more time to the main topic, the duty of righteousness toward others.

The correct answer couldn't be the third one, "Peace", because, although being at peace seems to be one of the speaker's objectives, he/she states that only by avoiding wrong deeds and always acting according to their duty to justice could the people reach and keep peace with other nations.

The correct answer couldn't be the fourth one, "Realization", because, even though the realization of the people's blessings could take them to feel like they are in a position to act right and help others, the main objective and topic of the speech are still fulfilling a duty.