420+180=____
68+200=____
750-300=____
7×0.7=____
7×0.7×0.7=____
7×0.7×0.7×0.7=____
7×0.7×0.7×0.7×0.7=____
7×0.7×0.7×0.7×0.7×0.7…____
下列数据中,与地球赤道长度最接近的是
常见的玻片标本有____ 、____ 和____ 三种。