<prompt> Floor of middle ear cavity is in relation with:Internal carotid arteryBulb of the internal jugular veinSigmoid sinusRound window  <response>: b Bulb of the internal jugular veinRef. Cummings, 6th ed., 1983The floor of middle ear cavity is a thin plate of bone separating the middle ear from jugular bulb below.Internal carotid artery is in relation to the anterior wall of middle ear.Sigmoid sinus is not related directly with middle ear cavity. It lies posterior to the mastoid antrum.Round window lies postero-inferiorly on the medial wall of middle ear. 