48. once again：再一次
e.g. I want to try this once again.
once and again：一再
e.g. I have told him once and again not to do that.
49. out of question：毫无疑问，必定
e.g. Out of question, this plan can be fulfilled ahead of time.
out of the question：不可能的
e.g. What you propose is out of the question.
50. refer to：提及，涉及
e.g. I would like to refer back to the first of my three points.
e.g. Coal is often referred to as food for industry.
51. search sb.：认真搜查某人身体
e.g. They searched him but nothing was found on him.
search for sb.：搜查某地为找到某人
e.g. They searched for him everywhere but failed.
52. settle down：落下；定居
e.g. The dust slowly settled down.
He has settled down in the countryside.
settle down to：专心致力于；逐渐习惯于
e.g. He settled down to his homework.
They settled down to a new job.
53. speak for itself：不言而喻
e.g. One does not to be told that this fact speaks for itself.
speak for oneself：发表本人的意见
e.g. What others think I do not know, I can only speak for myself.
54. submit to：屈服于
e.g. He has to submit to an operation.
e.g. They must submit the case to the court.