单语范例（未经PONS编辑处理）
Most hoses end with a bite valve that opens when the user bites down on it; the valve may be protected by a dust cover.
en.wikipedia.org It used a proprietary grip which attached to the upper portion of the frame (a metal part that comprised the dust cover and frame rails).
en.wikipedia.org The ejection port is normally closed with its own dust cover which opens automatically once the trigger is pressed.
en.wikipedia.org In some cabinets, a thin sheet of plywood is inserted into a groove in the web frame to serve as a dust cover between drawers.
en.wikipedia.org Heavy dust cover is also indicated by the high albedo (reflectivity) and low thermal inertia of the region.
en.wikipedia.org