If you left your book on the table overnight, you would find the following morning that it was still exactly when you had left it, provided nobody had moved it. If a ball is made to roll on a very smooth surface, it will roll a long distance unless something stops it or changes its direction. This tendency of an object to remain at rest unless something moves it and to continue moving unless something stops it is known as the Law of Inertia.
The following examples show the truth of this law.

• (a) Put a table-cloth on a table and arrange a pile of books on it. Hold one edge of the tablecloth and pull it quickly. The table-cloth will come off, leaving the pile of books undisturbed.
• (b) Place a small piece of cardboard on an open jar and place a coin on it directly over its mouth. Use one finger to flick the piece of cardboard away. You will notice that the coin drops into the jar.
• (c) Sitting in a car which starts suddenly, you feel you are jerked backwards. In fact, you are not jerked backwards. Your lower half, which is in contact with the cushion, is forced to move forward with the car, and the upper part of your body, which remained at rest, is left behind.

In the second example, when the cardboard is flicked away, the coin will ______.

A．drop into the jar

B．cover the mouth

C．stay on the cupboard

D．move into your hand

患者男性，29岁。右侧腹痛2小时，扩散至全腹部2小时急诊就医。体检：脉搏100份，体温37℃，呼吸24/分，BP：120/75mmHg，心肺未发现异常，腹肌紧张，全腹有压痛和反跳痛，肠鸣音低弱，可疑移动性浊音。血常WBC：13.2×10⁹/L，中性0.82。

检查提示：病人腹部平片见右侧腹较昏暗，未见明显膈下游离气影。血、尿淀粉酶不高。腹腔穿刺有少量淡绿混浊液，涂片有食物残渣及脓球。病史询问过去有上腹饥饿痛史。诊断为消化性溃疡穿孔所致全腹膜炎。该病人需行急诊剖腹探查术的主要理由是什么？（）

A.病人本次急性发病时间较短

B.腹腔化脓性感染尚不明显

C.疑有上消化道穿孔

D.溃疡病可能进行根治性手术

E.病员的内环境和生命体征尚相对稳定

F.病员尚无全身性病理生理紊乱