听力原文： The World Heritage Committee (WHC) overlooking conservation of global heritage sites will convene its annual meeting next week in Durban, South Africa, to review 42 proposed sites for inscription on the prestigious World Heritage List. Extensions for nine sites that have already been inscribed will also be proposed during the 29th session of the WHC under the United Nations Educational, Scientific and Cultural Organization (UNESCO), according to the organization's official website. The proposed sites include 28 cultural sites, 10 natural sites and 4 mixed sites presented by 44 countries, including Albania, China and the host country South Africa. How many cultural sites have been proposed for inscription on the World Heritage List?