单项选择题 Because of the high loads the bearing material is a tin- aluminum alloy bonded to a steel shellThe crosshead pin is highly polished to a （）.

单项选择题 The load on the crosshead pin is always （）, so it is the （）half of the bearing which is subject to wear.

单项选择题 Because the top of the connecting rod swings about the pin and changes direction each time the piston reaches mid-stroke, the relative speed between bearing and pin at mid-stroke is zero, （）to a maximum as the piston approaches top or bottom dead center and then （） back to zero again as the piston approaches mid-stroke and the connecting rod changes direction.