食品干制保藏是指脱水干制品在它的水分降低到足以防止腐败变质的水平后，始终保持低（）进行长期贮藏的过程。
参考答案：水分
On April 24, Tsinghua University ______ its 100th anniversary at the People's Great Hall in Beijing. [ ]
A. congratulated
B. celebrated
C. challenged
D. calculated
二极管峰值包络检波器，原电路正常工作。若负载电阻加倍，会引起（）.
A.惰性失真
B.底部切割失真
C.惰性失真和底部切割失真
