The Option key on the Mac is also known as the Alt key.

I love my Mac and you will love yours! (by Emilio Imparato)
The Option key on the Mac is also known as the Alt key.

Pour obtenir les caractères [ et ] sur le clavier du Mac, on utilise les touches Alt et Shift en combinaison avec ( et ) respectivement.
Similar to a previous post on the backslash, the brackets characters can be obtained with the key combination: