I am a new programmer currently studying at computer science. I have some good knowledge about some programming languages(C/C++, php, visual basic, java). But i want to be a master with just one language. Please can anyone suggest which language should i choose which should be fit for the future. I can give you a limited list from which you can choose for me. Please help me.

(1) C++
(2) JAVA (desktop, web or mobile??)
(3) PHP
(4) Dot Net Framework
(5) C#
(6) Python