A vehicle includes a slip detection section arranged to detect a slip of a driving wheel based on the rotation speed of the driving wheel and the vehicle speed, and an engine control section arranged and programmed to perform control to decrease the output of an engine when the slip of the driving wheel is detected by the slip detection section. Power is supplied from a USB host device to the USB client device with a first current limit. Also provided is a watermark embedding apparatus, a corresponding watermark detecting method and apparatus, and a method and system for detecting document integrity. In addition, the invention provides a stack assembly that comprises a plurality of trays each of which comprises a plurality of baskets. Also disclosed is a fuel cell incorporating the membrane. The second sort area includes a plurality of second sections.