REVIEW

Simple present and simple past (nivel medio-alto):

http://www.saberingles.com.ar/exercises/102.html

http://www.saberingles.com.ar/curso/lesson15/06.html

Frases negativas:

http://www.saberingles.com.ar/curso/lesson13/06.html

La hora:

http://www.saberingles.com.ar/curso/lesson08/06.html

Simple Past:

http://www.saberingles.com.ar/exercises/203.html

Simple Present (positive, negative and questions):

http://www.ejerciciodeingles.com/ejercicios-present-simple-rellenar-huecos/

Present Simple (multiple choice):

http://www.isabelperez.com/happy/tenses/exercises/present_1.htm