Concept:The word "wane" means a gradual loss of strength, power, or extent.Explanation:In the sentence, "wane" is used to express a reduction in vigour or intensity.The word closest in meaning to this is "decrease"."Dissipate" means to scatter or disappear gradually."Disappear" means to go out of sight completely."Deteriorate" means to become worse in quality.Only "decrease" directly matches the idea of a decline in amount or degree.Answer:D. decrease