A:to cut the watermelon with
B:to cut the watermelo
C:cutting the watermelo
D:cutting the watermelon with
——Did you hear that water in Tai Lake smelled terrible?——Yes.It ___________ because of people and factories.
小动物的遗体被深埋在了大树旁,经过较长时间后,遗体不见了,其主要原因是( )
某种溶液中存在Cu2+、Ag+、Ba2+三种金属离子,现用NaCl、NaOH、Na2CO3三种试剂分别使它们逐一沉淀分离出来,则所加试剂的正确顺序是( )
为了更有效预防佝偻病,补钙的同时还应添加( )