6.把$\frac{2}{3}$:2=1:3改写成2×1=3×$\frac{2}{3}$是根据( )
| A. | 小数的性质 | B. | 分数的性质 | C. | 比例的性质 | D. | 比的性质 |
5.6个同学握手,每两个握一次,一共要握( )次手.
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| A. | 12 | B. | 14 | C. | 15 | D. | 18 |