One of the challenges in video streaming is how to stream content to hundreds of thousands of simultaneous users. What are the options that companies( e.g. YouTube) have to overcome this challenge? (Choose all that apply.)

.	nothing can be done to overcome this challenge as every day millions of users use video streaming.
	b.	Use a single, large video mega-server
	c.	Store/serve multiple copies of videos at multiple geographically distributed sites
	d.	push CDN servers deep into many access networks of ISPs all over the world