1. 强调；凸显
    If one thing, for example an action or an event, underlines another, it draws attention to it and emphasizes its importance.

    e.g. The report underlined his concern that standards were at risk...
           报告强调了他对道德水准可能会受影响所表示的关注。
    e.g. The decision to keep him in hospital for a second night underlines the seriousness of his injury...
           让他在医院再住一晚的决定表明了其伤势的严重性。

2. 在…下画线
    If you underline something such as a word or a sentence, you draw a line underneath it in order to make people notice it or to give it extra importance.

    e.g. Underline the following that apply to you...
           在符合自身情况的项下画线。
    e.g. Take two coloured pens and underline the positive and negative words.
           用两支彩笔分别在表示肯定和否定意义的词下面画线。