Analysis
Context: The sentence structure suggests a behavior (i) by advocates, a trend (ii), and a resulting fear that their message (iii) will be compromised.
1. Analyze the Trend and the Message:
- Trend: The number of smokers per capita since the 1970s.
- Message: The campaign's message is "predicated on dire predictions." (i.e., warning of terrible future health outcomes).
- Fear: The advocates are doing (i) because they are "aware that, lest this trend reverse itself, their message... is likely to be more (iii) ________ than one rooted in reality."
2. Determine Blank (ii) - The Trend:
- If the message is predicated on dire predictions (i.e., things are getting worse), but the reality is that the message might become less effective if the trend continues, the trend must be positive (fewer smokers).
- E. beein drammatically bellooning: Grammatically incorrect and means increasing. (Opposite)
- D. remain unchanged: Would not lead to their message being undermined.
- F. been steadily decreasing: If smoking rates are dropping, the dire predictions seem less urgent or less likely to come true, which undermines the message. This fits the contrast.

Choice for (ii): been steadily decreasing.
3. Determine Blank (i) - The Advocates' Action:
- The advocates have a message based on dire predictions, but the reality is that smoking is decreasing (Blank ii). Therefore, they must be trying to avoid highlighting the positive reality, as it would weaken their fear-based message.
- A. quick to cite: They would cite this fact only if it supported their dire message (it doesn't).
- B. reluctant to acknowledge: They are unwilling to admit the positive trend because it undercuts their message. (This fits the "perhaps aware that..." clause.)
- C. indifferent to: Their actions suggest they are not indifferent; they are making strategic choices based on awareness.

Choice for (i): reluctant to acknowledge.
4. Determine Blank (iii) - The Resulting Message Quality:
- If the positive trend (decreasing smokers) continues, the message based on dire predictions is likely to be more (iii) ________ than one rooted in reality. A message not rooted in reality is considered false, manipulative, or ineffective.
- G. harmful: The message itself isn't necessarily harmful.
- H. disingenuous: Not completely honest or sincere. A message based on predictions that don't match the current trend could be seen as dishonest or manipulative. (Good fit, but check I.)
- I. efficacious: Producing the desired effect; effective. The sentence structure is complex: The message based on predictions will be more (iii) than one rooted in reality. The comparison is between two types of messages. If they avoid the decreasing trend, they want their message to remain effective. However, the passage implies their message will be less effective if the trend continues. Wait, re-read the final clause carefully: "...their message, which is predicated on dire predictions, is likely to be more (iii) than one rooted in reality."
- If we use the standard interpretation of the original sentence from which this is drawn, the intended meaning is that they fear their dire message will be exposed as false or less effective than a realistic one.
- Let's test the pair (i) reluctant to acknowledge and (ii) steadily decreasing with the structure:
- If the smoking rate is decreasing, the dire predictions look weaker. They fear their message will be seen as disingenuous (H) compared to a message that acknowledged the reality.
- Let's consider the possibility that the text is implying that dire predictions are more effective than realistic ones, which is why they are reluctant to acknowledge the truth:
- The message (dire predictions) is likely to be more efficacious (I) than one rooted in reality. This would mean they are being manipulative, believing fear works better.

- Given the negative context of "dire predictions" being undermined by reality, $\mathbf{H}$. disingenuous (meaning insincere or false) is a strong fit for what they fear their message will become if they continue to ignore reality. However, option I. efficacious is often the intended answer in this specific sentence structure, implying they fear losing their most effective tool (fear-mongering) if they admit the trend is positive.
- Let's go with the interpretation that they fear their message will be exposed as false/insincere (H) because they are ignoring the positive trend (F).