例：keep between the two of us 不让第三者知道，保密
Model：
——What I'm going to say is rather personal，so let's keep between the two ofus.(我要讲的纯属私事，所以希望你能保密。)
例：scratch the surface 只懂皮毛，很不了解(通常和限制性副词如only, hardly等词连用)
Model:
——You've certainly done a lot of research for yourproject.(你显然对你的课题做了不少研究。)
——It seems like a lot, but actually I've only scratched thesurface.(看上去不少，但事实上我只懂一些毛皮。)
例：up in the air 尚未决定的;捉摸不定的;悬而未决的
Model:
——Her plans for the weekend are still up in the air.(她尚未决定如何度过这个周末。)