分类：教育/科学-理工学科-生物学
问题：Bi和Di？表示双的时候何时用Bi
表示双的时候何时用Bi-何时用Di-？
回答：Bi-:两次；两倍；双
Bi- is used at the beginning of nouns and adjectives that have `two' as part of their meaning. 
Bi- is used to form adjectives and adverbs indicating that something happens twice in a period of time or happens once in two periods of time that follow each other.

Di-:含有两个原子的；含有两组…物质的
containing two atoms or groups of the type mentioned