Meyer and his team were the first ______ how the disease spreads from animals to humans.
A:showing
B:show
C:to show
D:shown
读“我国人口结构变化趋势图”,回答下面小题。
两条相对的经线组成一个经线圈,可以把地球分为两个半球.请根据所学知识,回答下面小题.