WP8 await and async Issue

WP8 await and async Issue

In my coding, i have 4 tasks. Task A Task B Task C Task D
Task D need to be executed after finish of Task A ,B &C Task A , Task B
,Task C are Independence and can execute at the same time
i am now using a sequence approach to perform the action, it take very slow
await Task A;
await Task B;
await Task C;
await Task D;
I would like to know if i can make it run concurrently and After finished
Task A,B,C ,it will run Task D
Thanks for your help .