A

    When I was four, one day I was playing outside our house. I saw my grandfather's truck. It was black and looked better.” I got some paint and a brush which were left in the kitchen by my father. I painted the truck white and blue all over. I was finishing the job when my mum walked up and stopped me. She was worried that my grandfather would be angry. However, when my grandfather looked at my paintings on the truck, he laughed loudly. “Angela, that's the prettiest truck I've ever seen! I love it!”

    Sometimes adults (成年人) don't stop to see things through children's eyes. They missed so much beauty in the world. Luckily, my grandfather saw things in another way.

下列各组元素中，按最高正化合价递增顺序排列的是（　　）

如图反映的是中国城镇人口数的变化情况。其中，导致从E到F变化的主要原因是（    ）