单项选择题
What was the main harmful effect of the pest killer DDT on bald eagles（）
A．It limited their supply of food. B．It killed many baby bald eagles. C．It destroyed many of their nests. D．It made their eggshells too fragile.
单项选择题 What are the speakers doing（）
单项选择题 What happened in London a few months ago（）
