单项选择题 The engine is reversed by axial displacement of the camshafts In order for this to be carried out, the cams are （） with inclined transition faces.

单项选择题 The engine has one or two group of fuel pumps, depending upon （）.

单项选择题 The energy for pushing this piston up can be supplied from （）, so that the piston can keep moving up and down.