Thanks for both of you guys, the first one gives me much detail on which models has 802.11n, and second one gives me a very clear instruction to get to it.
how do you take screenshot in mac??
Take a picture of the whole screen
?-Shift-3
Take a picture of part of the screen
?-Shift-4, then drag to select the area you want in the picture.
To cancel, press Escape.
Take a picture of a window, a menu, the menu bar, or the Dock.
Press ?-Shift-4, then press the Space bar. Move the pointer over the area you want so that it's highlighted, then click.
To drag to select the area instead, press the Space bar again. To cancel, press Escape.