Power in China

My mother is under the impression (no sources, just an impression) that hotels in China will have outlets identical to those in the US. My father is under the impression that every city will have a different type of outlet (shape of plug, voltage, frequency) from every other city. His only source is Wikipedia, which appears to directly contradict what he says (it says all of China uses one particular type of outlet).

Anyone know the reality and/or have reliable sources? We're starting in Beijing, traveling across the NW of the country, then flying to Shanghai and Hong Kong.