a) It's caused by bacteria. Pericoronitis is an infection. It's caused by normal oral bacteria, like those found in dental plaque. It's the gum relationship around a partially-erupted tooth that allows pericoronitis to occur.
A futures exchange or futures market is a central financial exchange where people can trade standardized futures contracts; that is, a contract to buy specific quantities of a commodity or financial instrument at a specified price with delivery set at a specified time in the future. These types of contracts fall into the category of derivatives. The opposite of the futures market is the spots market, where trades will occur immediately (2 business days) after a transaction agreement has been made, rather than at a predetermined time in the future.
A forward is like a futures in that it specifies the exchange of goods for a specified price at a specified future date. However, a forward is not traded on an exchange and thus does not have the interim partial payments due to marking to market.Nor is the contract standardized, as on the exchange. put is the option to sell a futures contract, and a call is the option to buy a futures contract. For both, the option strike price is the specified futures price at which the future is traded if the option is exercised. Futures are often used since they are delta one instruments.