1. If we don't operate on your wife, there's a good chance she'll die. Time is of the essence. Please make a decision now.2. The government must start investigation immediately; time is of the essence.3. We must catch the suspect before he leaves the country. We are on a clock now.
 Time is of the essence. We don't have much time. on a clock是正統的美語說法.We are on a clock = We are in a hurry = 我們很趕或很急
1. 如果你太太現在不動手術, 死亡機率很高, 時間緊迫, 請你儘快做決定.2. 政府一定要立即調查, 刻不容緩.