A、Shade of sunlight. B、Light pollution. C、Loss of sleep. D、Business competition. B题干询问说话者认为什么影响了人们的生活。对话中提到，研究者们指出灯光指示牌造成了广为人知的光

This is the central district and it’s 11 o’clock at night time but if I put on my sunglasses it wouldn’t be too dark at all and that’s because there are lights everywhere. There’s a decorative lighting sign across the street at an old antique shop. It’s closed but there are one, two, three signs lit up and it’s the same thing all down the street.
     (20)Now, researchers say that the signs are contributing to what is known as light pollution—you can tell by looking up into the sky. Not a single star in sight. In fact the sky is a light shade of grey because of the amount of light in the central district and(20)this is affecting people’s lives because above these businesses and signs are apartment blocks. So these lights are reflecting off the windows and bouncing into people’s homes. Christine Siu lives near the area. She says sometimes the lights are so bright that they make it hard for her to fall asleep.
    Well,(21)researchers are asking businesses to dim their lights and to turn them off earlier in the evening except it’s not going to be an easy thing to do. Actually, many big cities are places where businesses can offer the same services or sell the same products side-by-side.
     (22)The only way they can distinguish themselves from their competitors is through these decorative lighting signs to grab customers’ attention. The bigger, the brighter, the better. Some big cities are known to be places that never sleep. Well now it seems that’s because they never allow the sky to go dark.
20. What does the speaker say is affecting people’s lives?
21. What are researchers asking businesses to do?
22. Why do the businesses turn on the decorative lighting signs?