What is the 10-20-30 rule for slideshows from Guy Kawasaki of Apple?

A、Slideshows last no more than 10 minutes; should contain no more than 20 slides; and use a font size of no less than 30 point.;
B、Slideshows should use a font size of no less than 10 point; contain no more than 20 slides; and last no more than 30 minutes.;
C、Slideshows should contain no more than 10 slides; use a font size of no less than 20 point; and last no more than 30 minutes.;
D、Slideshows should contain no more than 10 slides; last no more than 20 minutes; and use a font size of no less than 30 point.