烟酸缺乏病是由于饮食内缺乏()和()致。临床表现三联征为()()()。皮损最好发于()。
参考答案:烟酸;色氨酸;皮炎;腹泻;痴呆;手背
Japan's refusal to release ________ Chinese fishing boat captain had caused ________ serious
damage to SinoJapanese bilateral contacts (双边交往). [ ]
A. a; /
B. a; a
C. the; /
D. the; the
滤波电路的作用是改善()的平直程度并减少交流成分。