如果a+b=0，那么a、b两个数一定是______关系．
如果a+b=0，即a=-b，那么a、b两个数一定是互为相反数关系．
故答案为互为相反数．
When _____, the museum will be open to the public next year. [ ]
A. completed
B. completing
C. being completed
D. to be completed
I really enjoyed your speech, ______ there were some parts I didn’t quite understand. [ ]
A. because
B. for
C. until
D. though
