双务法律行为
参考答案：
指当事人双方互享权利互负义务的法律行为。
She looks sad. Could you please tell me ____ that prevents her from being as happy as before?
A．what it is
B．it is what
C．how it is
D．it is how
非法定继承人根据遗嘱承受的房地产，免缴契税。 ( )
