A:pointed to
B:pointed out
C:pointed at
D:pointed off
2Na3PO4+4CuSO4+2NH3•H2O=Cu4O(PO4)2↓+3Na2SO4+(NH4)2SO4+H2O
请回答下列问题:
若x-2y+9与|y﹣3|互为相反数,则x+y的值= ____
下列属于动物先天性行为的是( )