The word “handily” in this sentence is best replaced by the wordA eventually.B slowly.C never.D smoothly.

The best replacement for “handily” in the sentence is D, “smoothly.”

Explanation: “Handily” means doing something easily or without difficulty, which aligns closely with “smoothly.” The other options do not convey the same meaning. “Eventually” implies a delay, “slowly” suggests taking more time, and “never” indicates impossibility, none of which fit the original context.