What is the difference between the upfront and the scatter market?

Choose one $2$ points

The scatter market occurs throughout the entire year so it is when most television commercial inventory is transacted

The scatter market allows advertisers to buy the inventory they most want on demand AND gain audience guarantees

They are essentially the same, it just depends on whether or not an advertiser wants to commit their dollars upfront or throughout the year

The upfront market is when $80\%$ of all television inventory is sold AND affords advertisers audience guarantees