Derailleur gears by 13 drive-train. Most road bicycles have two chainrings, and touring bicycles commonly have three. The rear derailleur serves double duty: moving the chain between rear sprockets and taking up chain slack caused by moving to a smaller sprocket at the rear or a smaller chainring by the front derailleur. In order to accomplish this second task, it is positioned in the path of the bottom, slack portion of chain. Sometimes the rear-derailleurs are re-purposed as chain tensioners for single-speed bicycles that cannot adjust chain tension by a different method. Although variations exist, as noted below, most rear derailleurs have
Word sort - their spelling or orthography - the more efficient and fluent their reading will be. Word sorts place instructional emphasis on the exploration of patterns that can be detected in the sound, structure, and meaning features of words. Thus, word sorts contribute to orthographic or spelling knowledge, the engine that drives efficient reading as well as efficient writing. There are three different types of word sorts: sound sorts, picture sorts, and word sorts. Sound sorts can take on many forms in a primary classroom and this is essential because sound is the first layer of English orthography. Sound study can