a.[B]

1. 兩的，雙的
   dual ownership

   兩人共有

2. 雙倍的；雙重的
   a dual nature

   雙重性

n.[C]【文】

1. 雙數
2. 雙數詞

adj.

1. consisting of two parts, elements, or aspects.
   ▸Grammar  denoting an inflection that refers to exactly two people or things.
2. (often dual to) Mathematics  related to another theorem or expression by the interchange of terms, such as ‘point’ and ‘line’.

n.

1. Grammar  a dual inflection.
2. Mathematics  a theorem or expression that is dual to another.

v.