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A. Tips are not usually included in the total check.
B. A 15 percent tip in large cities indicates satisfactory service.
C. People tip waiters and waitresses.
D. People always put tips on the table.

A. laser-doppler 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-doppler radar