If you need a "preposition", I would guess "of" is the answer. But if you were open to any word, then I would fill the blank with the word "predicting". "the receipt" is singular, but not a noun, it's a verb "echoes" is plural, and is a noun. So I would guess the answer you're looking for is "plural noun". We don't need to say "the receipts" because we are not talking about the noun (the physical object) of receipt/receipts. We are talking about the verb (the activity) to receive, where "the receipt of" means "the receiving of".

One receipt, many echoes. It makes no difference that the noun "receipt" is singular and the noun "echoes" is plural: "A coat of many colors" "A performance of many symphonies" "A bonfire of vanities" "A thousand examples of a missing person" "The weather forecast is: showers and overcast skies." "The weather forecast calls for showers and overcast skies."

1. The weather forecast is for showers and overcast skies. * Why: The preposition "for" is used because it indicates what is expected or predicted in the weather forecast. We commonly say "the forecast is for rain," "the forecast is for snow," etc. 2. "The receipt of echoes" is considered a singular noun. * Why: The word "receipt" is singular, and in this phrase, it refers to the act or instance of receiving echoes. "Echoes" is plural, but it doesn't change the fact that "receipt" is a singular noun referring to the overall process of receiving. The phrase "the receipts of echoes" would imply multiple instances or documents of receiving echoes, which is less common in this context.

1. I don't think it needs a preposition in this case, I thought you might mean "scattered" showers. No preposition is necessary. 2. "Receipt" is singular "Echoes" is plural. Receipt is a verb from receive - that is my understanding. I would have to know more of the context.