3.1

Question 1

android

Answer 1

open handset alliance
open source
based on linux

Question 2

ios

Answer 2

apple proprietory
closed source
based on unix

Question 3

adroid sdk

Answer 3

software developers kit
creates apps
makes them available on google play
you can also download on third party sites (sideloading)

Question 4

ios app store

Answer 4

strictly controlled by apple