I _______ the MP player since two years ago.
A:bought
B:have bought
C:have
D:have had
悠悠文明史,漫漫丝绸路.我国素来以“缫丝养蚕”著称于世.你可知道蚕丝是家蚕发育过程中哪一时期的杰作( )