+ LANGUAGE CONTENT:
+ To introduce two sounds / s / and / z / and to revise the previous grammar: tenses
+ LANGUAGE FUNCTION:
+ To enable the sts to pronounce two sounds / s / and / z /
+ To enable the sts to do the exercises, using the right tenses
+ EDUCATIONAL AIM:
+ To have the sts be familiar with the new sounds and revise the previous tenses
* Structures: past simple, past progessive and present perfect.