一、单词拼写。
结合语境，根据汉语提示用单词的适当形式填空。
1. In a written ________ (道歉), the BBC admitted they had misled the public.
2. Can you make the dog stop ________ (吠叫) at the mailman?
3.During these periods the birds will lie on the ________ (笼子) floor as if trying to lay or hatch eggs.
4.A holiday isn't an ________ (可有可无的) extra. In this stressful world, it's a must.
