计算:12+(-4)+(-16)+8.
原式=(12+8)+[(-4)+(-16)]=20-20=0.
― What are you ______ your suitcase for?
― I'm ready for a trip.[ ]
A. making
B. shutting
C. packing
D. putting
资源分解结构编码的英文缩写是( )。
A.PBS
B.WBS
C.RBS
D.CBS