Step 1: Understand the context.
- "Bat" refers to a specific, but indefinite, creature, so a is used.
- "Ground" is a generic term, so the is used to refer to a specific ground.
- "Weasel" is also specific here, so the is used.
- "Enemy" refers to a known concept and is therefore preceded by the.
- "Mouse" refers to a specific animal in contrast with the bird, so a is used.
Step 2: Check options.
- Option (D) correctly follows the pattern for definite and indefinite articles, making it the correct choice.
Therefore: The correct answer is \boxed{(D)}.