—In 1908 Lord Northcliffe offered a prize of £1,000 to the first man who would fly across the English Channel. Over a year passed before the first a____ was made.
甲、乙两物体质量之比是1:2,体积之比是4:1,同时从同一高度自由下落,则下落加速度之比和下落时间之比分别为( )
读我国四大地理区域分布图,回答下列问题