<prompt> Electron microscopy is helpful in diagnosis of -a Rotavirusb RSVc Herpesvirusd Prionaacadb  <response>: Rotavirus culture is difficultSo, electron microscopy is useful in diagnosis of Rotavirus infectionThey characteristically appear as little wheels with short spokes radiating from a wide hub to a clearly defined outer rim.The name Rota is derived from Latin word rota means wheel. 