B. She is a great singer, but she is also a great dancer.
C. He is a good teacher, but his classes are boring sometimes.
D. I love reading books, and I also love writing stories.
Explanation
He is a good teacher, but his classes are boring sometimes.
Explanation: The clause "but his classes are boring sometimes" contrasts poorly with "he is a good teacher." It introduces a contradictory statement that diminishes clarity.