Contrast may make something appear more beautiful than it is when ________ alone. A) seen B) is seen C) to be seen D) having been seen為什么不選B，而選A，請回答詳細(xì)一點(diǎn)
熱心網(wǎng)友
如果when 后面有主語，例it，那就是選Ｂ，如果省略了主語，也要省略is
熱心網(wǎng)友
簡潔！如果是用B,應(yīng)該：when it is seen alone.
熱心網(wǎng)友
簡潔！如果是用B,應(yīng)該：when it is seen alone.