Hi everyone! We’ve been discussing this subject in class, but I thought you might like to have some more practice in it.
In the first place, did you know that you can send in your grammar doubts to the BBC English service, and they’ll answer them for you? Here is an example of a student who wanted to know about cleft sentences.
Here you have an online exercise to order the elements of a cleft sentence, in case you feel you need some more practice.
On the other hand, why not read this explanation about adding emphasis in English? It covers other structures apart from cleft sentences.
Finally, here you have a video on how to take care of your vocal expression in presentations. Enjoy!