Explanation:

Introduction:
In the given statement, the phrase "sufficient silent communion" refers to a shared understanding or connection between two individuals without the need for verbal communication. The narrator suggests that there has been enough unspoken understanding between Framton and someone else.

Understanding the Context:
To determine the correct answer, we need to analyze the context and identify the possible characters mentioned in the passage. The options provided are:
(a) Sappleton
(b) Mrs. Sappleton
(c) Ronnie
(d) Vera

Analysis:
1. Sappleton: Sappleton is mentioned as a possibility. However, there is no evidence in the given statement or context to suggest that the silent communion is between Framton and Sappleton.
2. Mrs. Sappleton: Mrs. Sappleton is another possibility. As the wife of Sappleton, she could potentially share a silent communion with Framton. However, there is no direct reference to Mrs. Sappleton in the given statement.
3. Ronnie: Ronnie is not mentioned in the given statement, making him an unlikely option.
4. Vera: Vera is a young girl who tells Framton a fictional story about the open window. In the context of the given statement, it is implied that the silent communion is between Framton and Vera. The phrase suggests that they have a mutual understanding without the need for spoken words.

Conclusion:
Based on the analysis, option (d) Vera is the correct answer. Framton and Vera have developed a silent communion through their shared understanding and unspoken connection.