情态动词shall和should的用法比较：
时态：
“shall”主要用于第二人称和第三人称，表示未来的承诺、警告或命令。
“should”用于第一人称，表示义务或道德上的责任。
例句：
He shall pay for his mistake. (未来承诺)
You should apologize to her for your behavior. (道德责任)
语气与强度：
“shall”通常带有更强烈的语气，尤其在法律、合同或正式文件中，表示强制或义务。
“should”相对温和，更多用于建议或推荐。
例句：
According to the law, you shall appear in court on that date. (法律义务)
It is recommended that you should eat a balanced diet. (建议)
虚拟语气：
在虚拟语气中，“should”常用于第一人称和第三人称，表示与现实相反的情况。
“shall”在虚拟语气中不常用。
例句：
If I had known the answer, I should have won the prize. (与现实相反的情况)
习惯用法：
“should”有时用于表示惊讶、不相信或失望。
“shall”有时用于表示威胁或警告。
例句：
You shouldn't have done that! (表示惊讶)
If you continue to misbehave, you shall be punished. (威胁)
练习题：
The judge _______ sentence him to death, but gave him a lenient punishment instead.
A. shall B. would C. could D. should
答案：A
If I _______ known the answer, I _______ the exam easily.
A. had; would pass B. would; would have passed
C. did; would have passed D. had; would have passed
答案：D
