1) Explanation

Let's break down the sentence to understand the context and the meaning required for the blank:
- "The seemingly $\qquad$ community of retirees was actually a hotbed of controversy,..."
- The crucial word here is "seemingly" followed by "actually." This sets up a direct contrast. What the community appears to be is the opposite of what it actually is.
- What it "actually" is: "a hotbed of controversy, as issues ranging from lawn care to shuffleboard sparked fierce debates." This describes a community that is full of conflict, arguments, and disagreements.
- Therefore, the blank must describe what the community appeared to be - the opposite of controversial, argumentative, or filled with fierce debates. It must appear calm, peaceful, or harmonious.

Let's evaluate the given options:
- A. chivalrous: Relating to the ideal knightly qualities of courtesy, courage, and honor. This describes behavior, not the overall atmosphere or nature of a community in terms of conflict.
- B. cynical: Believing that people are motivated purely by self-interest; distrustful of human sincerity or integrity. This describes a disposition, not a lack of controversy.
- C. sincere: Free from pretense or deceit; honest. This describes honesty, not peacefulness or harmony.
- D. fervid: Intensely enthusiastic or passionate, especially to an excessive degree. This describes a strong emotion or intensity, which could even align with "fierce debates," not oppose "controversy."
- E. placid: Not easily upset or excited; calm and peaceful, with little movement or activity. This perfectly describes the opposite of a "hotbed of controversy" and "fierce debates." It fits what the community would "seemingly" be.

Conclusion:

The contrast established by "seemingly...was actually" requires the blank to be an antonym of "hotbed of controversy" and "fierce debates." "Placid" (calm and peaceful) fits this perfectly.

The final answer is $\square$ E .