【简答题】Holidays are often associated with no work and all play. People seek to enjoy their holidays in different ways. Vacation packages (一揽子交易) have been in existence for a long time. ---小题1:--- So now peop...
【单选题】听力原文:Stem cells are undeveloped human cells that can grow into many or all of the different specialized cells in the human body. Although stem cells have been harvested from adults, the most versatile...