Read the following sentence carefully and select the pair of words from the given choices that appropriately fills the two blanks to render the statement grammatically correct and meaningful.

The delegates _______________ in the main hall to hear the keynote speech and _____________ the new international agreement.

The correct pair of words to complete the given sentence is assembled, ratify.

Step 1: Analyze the context of the sentence
The sentence describes two logical actions performed by delegates regarding a conference or official gathering:
1. Coming together in a central space ("main hall") to listen to a speaker.
2. Taking a formal legal/official action regarding a new international agreement.

Step 2: Evaluate the first blank
The phrase "in the main hall to hear the keynote speech" requires a verb indicating that the delegates gathered together. The word assembled means gathered together in one place for a common purpose, which logically fits delegates entering and gathering in a main hall.

Step 3: Evaluate the second blank
The second blank follows "and", maintaining parallelism with the base verb form "hear" ("to hear... and [to] _____________"). In the context of an international agreement, ratify means to give formal consent to a treaty or contract, making it officially valid. This completes the thought meaningfully and grammatically.

Step 4: Review incorrect choices
• departing, sign: "departing" is a participle that does not fit grammatically as the main past-tense verb of the sentence, and delegates do not depart into a hall to hear a speech.
• remained, remaining: "remaining" creates grammatically incorrect parallelism following "to hear".
• scattered, draft: "scattered" means to disperse in different directions, which directly contradicts gathering in a hall to listen to a speech.
• dismissed, cancel: "dismissed" implies being sent away rather than gathering to attend a keynote address.

Thus, inserting assembled and ratify results in a complete, coherent, and grammatically correct sentence: "The delegates assembled in the main hall to hear the keynote speech and ratify the new international agreement."