All of these words are a type of sport. This means we have to think about what makes each sport unique. In this case, "football" is the only sport on the list that does not use a round ball. 

"Silt" does not belong with the other words. "Silt" is a type of fine sand or dirt, usually found in a body of water. All of the other words are types of geographic features. A "plateau" is a relatively flat place of high ground. (Think of a hill or mountain with the top cut off.) A "mountain" is a large, steep hill. A "delta" is usually a triangular shaped deposit of rich sediment at the mouth of a river. A "coast" is where any land meets the ocean.

Although all of these words are a type of vegetable, "beets" are red. All of the other vegetables listed are green.

"Pizza" does not belong with the other words because it is not a kind of dessert. All four of the other words are eaten for dessert. ("Mousse" is a kind of creamy pudding.)

"Canada" does not belong with the other words because it is a country, while of the other words are continents. There are seven continents: Asia, Africa, Australia, Antarctica, Europe, South America and North America. "Canada" is a country in North America. "Australia" is both a country and a continent.

All of these words are a type of plant. "Corn" is a grain. "Marigolds," "pansies," "daisies" and "roses" are types of flowers. "Corn" does not belong with the other words.

All of these words describe a family member. "Brother" does not belong with the other words because it describes a male family member. "Grandmother," "mother," "aunt," and "sister" all describe female family members.

All of the related words pertain to some kind of subsequent presentation of an event. A reverberation or an echo are the “replayed” sound of some original action of making a noise. A reflection is the redisplaying of an image—as in the mirror that reflects an image that first was “in” the person seen therein or in a metallic surface that reflects light that had originated from another source. Finally, even a vestige is a “representation” of something, for it is a “leftover” that outlasts an original event. (A footprint is a vestige of an action of walking that happened before. Indeed, “vestige” comes from the Latin for footprint). Only “utterance” describes an originating, non-repeated, non-representational activity.

All of the related words here have to do with some process of “standing between” two things. Someone “mediates” by attempting to help two parties agree. (More generally, the term can mean “to be a link between two things”). An intervention is an action by which something is stopped by means of some obstacle (literally or metaphorically). To translate is “carry” the meaning from one language to another. (The “-late” portion " the word literally means “carry”!). To insinuate can mean “to make a suggestion indirectly;” however, it can also mean “to manipulate a situation so as to place oneself into some favorable position.” Only “operate” does not convey this sense of “mediation” found in all the other options.

Each of the related words describes some action of making an idea more specific or explicit. For instance, to specify the details of an order is to “spell out” the exact details of that order.  A description can be seen as an itemizing or something in order to make it known in its details. When we “determine” to do something, we choose a certain actual thing to do after having had a number of potential activities. To explicate is to explain, often implying detailed analysis. Only “recount” has little to do with any of these other words. It means to “retell” as in “recounting a story.” This might be a nice detailed account, but the word does not necessarily signify such detail.