单选题 Implied but not stated ______.

A、 Laser-dopple radar is more accurate than microwave radar
B、 Microwave radar may not ensure absolute precision in measuring varying speeds
C、 The light-beam radar can measure only slow speeds with accuracy
D、 Microwave radar operates at a higher frequency than laser-dopple radar

【正确答案】 B

【答案解析】根据第一段第二句及第二段第一句可推断B正确。A项已在文中明确提出过，C和D项与原文相反。