Ejercicio 004

How long have you been in the United States?

Have you been working in this restaurant for ten years?

How long have you been learning English?

What have you been buying?

Have you been waiting here for two hours?

What have you been doing for the last 30 minutes?

Have your been exercising lately?

What have you been doing?

Have you only been waiting here for one hour?

How long have you been waiting for me?

Has she been telling people not to go to that shop?

http://ingles.about.com/od/gramatica/a/Presente-Perfecto-Continuo-ingles-present-Perfect-Continuous.htm

http://www.englishpage.com/verbpage/presentperfectcontinuous.html

http://www.shertonenglish.com/resources/es/passive-voice/modals-have.php

https://www.englishclub.com/grammar/verb-tenses_present-perfect-continuous.htm

http://www.inglessencillo.com/presente-continuo

http://en.wikipedia.org/wiki/Mark_Twain

http://www.elpuercoespin.com.ar/2013/11/02/la-novela-que-mark-twain-escribio-desde-el-mas-alla/

http://en.wikipedia.org/wiki/How_Long_Will_I_Love_You%3F

http://www.letrastraducida.com/2013/09/ellie-goulding-how-long-will-i-love-you.html