1. 底线：关键字与识别字就是那些用英文字母、数字与底线 (underscore) 所组成的「单字」. 「单字」与「单字」间以白空白来分隔是很自然的事;至於「单字」与符号,或符号与符号间的白空白就可有可无了.

2. 强调,在下面划横线：9. lot 小片土地 | 10. underscore 强调,在下面划横线 | 11. transit lines 运输线路

3.

3. 强调：undergo 经历,遭受 | underscore 强调 | underlying a.基本的

1. 强调；突出；强化
    If something such as an action or an event underscores another, it draws attention to the other thing and emphasizes its importance.

    e.g. The Labor Department figures underscore the shaky state of the economic recovery...
           劳工部的数据进一步印证了经济复苏状况的不稳定。
    e.g. The rash of accidental shootings underscores how difficult it will be to restore order here.
           一连串的意外枪击事件凸显了恢复该地区的秩序有多困难。

2. 在（字词、句子等）下画线
    If you underscore something such as a word or a sentence, you draw a line underneath it in order to make people notice it or give it extra importance.

    e.g. He heavily underscored his note to Shelley.
           他在给谢利的便条内容下面重重地画了线。

1. a line drawn underneath (especially under written matter)

    Synonym: underline

1. draw a line or lines underneath to call attention to

    Synonym: underline

2. give extra weight to (a communication)

    e.g. Her gesture emphasized her words

    Synonym: underlineemphasizeemphasise