Which of the following belong to sharing economy? A: OFO B: Didi Chuxing C: Tik Tok D: Airbnb

You can sign _______ for a free Tik Tok account to stay connected to family and friends. A: up B: into C: at D: on

If you love watching music video clips, you’d better visit<br/>________.() A: Taobao B: Q-zone C: Xiaohongshu D: Tik Tok

以下选项中，（）不是设计引物时常使用的软件和方法。 A: Primer BLAST B: Premier Primer 5 C: Primer BANK D: Tik Tok