Which of the following words best describes a contract that is legally acceptable and properly authorized?
答案解析
**Core Concept:** Adjective usage and context-specific meaning (valid).
**Analysis:** The correct answer is **B. valid**, as it directly means 'legally binding or effective'.
- **A. vain** refers to excessive pride or futility.
- **C. vacant** means 'empty or unoccupied'.
- **D. utter** means 'complete' or 'to speak'. None relate to legal enforceability.
正确答案：B