The Prefix is Otterbox's least expensive iPhone case. The durable silicone, polycarbonate skeleton build of the OtterBox Prefix is thicker than the Commuter and Reflex, but also the least protective. The Prefix is a one-piece case, meaning that it does not snap in place like the Reflex .
carbon is considered tetravalent because it has four valence electrons the valence electrons are in the outermost shell of the atom and allows carbon to form four bonds to other atoms
In Prophase I of meisosis. A tetrad is also called a bivalent. This happens so that crossing over can occur between non-sister chromatids. Crossing over is a source of genetic â¦ variability in the resulting daughter cells, gametes.