因时而变、随时而制与时时皆行,体现了与时俱进。 ()
当总效用增加时,边际效用应该()。
A. 为零
B. 为负数,且不断增加
C. 为正数,但不断减少
D. 为负数,但不断减少
All microcomputer CD-ROM drivers can play audio compact disks.
With the two advances in computer technology, a single processor can execute an instruction in 0.002