twobitadj.便宜的twonum.二；两个two-way charge双向收费Two-site ELISA双抗体夹心ELISA法two trace method双线扫描法two-pass grate二段式链篦机two-fluid cell两液电池two-place verb双项动词two-way system双向体系two-glass test两杯试验two-stage risk两阶段风险two-win theory双赢理论