How to zoom in and out of web pages and photos in iPad?

A、Slidingafingeroverthedisplayfromthebottomtotop,orviceversatogoback.;
B、Swipingafingeracrossthescreen.;
C、Double-tapping.;
D、Placingtwofingersonthescreenandspreadingthemfartherapartorbringingthemclosertogether,agestureknownas"pinching".