The number of output for a decoder if the input is 4

Explain why it is reasonable to assume that receiving 3 duplicate acks in tcp is an indication that the network is not currently congested.

I'm taking a class on how to make a movie, and it offers some apps that would be in the process. the thing is, i don't have any of those ha. if you have any tips on some apps i could use, that would be awesome. i don't have an iphone, so don't suggest any apps like imovie. i know that this is a weird question, but it would be super for me. : )

Under which key category do the page up and page down keys fall? page up and page down keys fall under the keys category.