how to save a excel 2008 graph into tiff pix

I tried to save my excel plot as a tiff file. However, when I clicked on the "save as", I didn't see "tiff" as a optional extension. Anyone knows how to do this?

You can save it as a different type of image and then convert it using Preview. Just right click the chart, choose Save as Picture…, and then save it as either a PDF or PNG (any format will work, but those will generally be the best quality). Then double-click the picture you saved in the Finder, and it should open in Preview. From there, choose Save As… and save it as a TIFF.

Thanks, nabl! It works.