The answer is B: Taxpayers have spent millions of dollars on programs to improve education.
This sentence (B) improved the fluency of the original sentence because it is organized in a direct order. First the subject (Taxpayers), and then, the predicate (have spent millions of dollars on programs to improve education.) It's clear and easy to understand, differently from the unnecessary use of the Passive Voice: "Millions of dollars have been spent by taxpayers on programs to improve education."