FOR VERSUS SINCE

For / Since

Ambas preposiciones se utilizan para indicar la duración de una acción:
Since: indica el comienzo de la acción. La acción se prolonga hasta el momento en que habla el emisor.  Significa “desde” una fecha concreta: día, mes, año, período del año (verano, invierno, el año pasado) , momento determinado.
For: señala la duración de la acción, prolongación en el tiempo.
Ejemplos:

I have been living in Seville since last june (y sigo viviendo)

I haven't seen you since last week (y hasta este momento no te he visto)

Yesterday I studied for three hours

I have been living in Seville for 1 year

I haven't seen you for a week

Exercises
1.- Completa las siguientes oraciones con "for" o "since".

	1.	……………………………………		I have been studying mathematics ________ three hours
	2.	…………………………………….		George has worked in this company ________ 8 years
	3.	…………………………………….		The socialist party has been in power ________ March 2004
	4.	…………………………………..		This terrorist has been in prison ________ three years
	5.	………………………………….		My mother has been travelling ________ last April
	6.	…………………………………..		The oil price has been going up ________ three months
	7.	………………………………		Alice has been in her bedroom ________ two hours
	8.	………………………………		We have been married ________ 1992
	9.	……………………………..		The socialist party has been in power ________ 6 months
	10.	………www,clasesinglesitalianolorenzini.com……………………..		What weather! It has been snowing ________ two days
	11.	…………………………….		It is unbelievable. They have been arguing ________ 6 o'clock
	12.	…………………………..		The oil price has been going up ________ last March
	13.	…………………………..		My French teacher has been ill ________ one week
	14.	……………………………		I have been studying mathematics ________ 4 o'clock
	15.	……………………………..		This terrorist has been in prison ________ 2001
	16.	…………………………….		My boyfriend has been sleeping ________ 7 o'clock yesterday evening
	17.	……………………………..		My mother has been travelling ________ 4 months