Final answer:
The excerpt from The Adventure of the Mysterious Picture that conveys the playful tone of the passage is option b) The detective grinned mischievously as he uncovered the hidden clues.
Step-by-step explanation:
The excerpt from The Adventure of the Mysterious Picture that conveys the playful tone of the passage is option b) The detective grinned mischievously as he uncovered the hidden clues. This excerpt uses the word 'mischievously,' which suggests a playful and lighthearted attitude. It indicates that the detective is enjoying uncovering the clues, and adds a sense of fun to the passage.