Step 1: Identify the source of the quote.
This line, "And gathering swallows twitter in the skies," is from *Ode to Autumn* by John Keats. The poem is a meditation on the beauty of autumn and the cycle of life.
Step 2: Analyze the options.
- (A) An Epitaph: Incorrect. The line is not from *An Epitaph*.
- (B) Macavity: The Mystery Cat: Incorrect. This line is not from T. S. Eliot’s *Macavity*.
- (C) The Soldier: Incorrect. This line is not from Rupert Brooke’s *The Soldier*.
- (D) Ode to Autumn: Correct. The line is from *Ode to Autumn* by John Keats.
Step 3: Conclusion.
The correct source of the line is *Ode to Autumn* by John Keats.