重点讲解：
1. at once 同时；一起；
例句：I dreamed up a plan to solve both problems at once.
我想出了一个方案，可以同时解决两个问题Rx.Zb_U+uz4wXiXghjq5。
2. in theory 从理论上说；照理说；
例句：In theory, the buyer could ask the seller to have a test carried out.
理论上，买方可以要求卖方进行一次测试;Zx&~FGYa17。
3. off-the-shelf 现成的；不用定制的；
例句：Any car you can buy off the shelf in a pastel pink has got to be saying something.
现货供应的任何一辆淡粉色汽车一定都有自己的卖点+[&RiZ|*Pqs%Tj&I。
4. for the time being 目前；暂时；
例句：I am staying at a friend's house for the time being.
我暂时寄宿在朋友家里Cs-U-2P%]tO*^y。