HTML5 的正确 doctype 是？
A<!DOCTYPE html>
B<!DOCTYPE HTML5>
C<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 5.0//EN"
D"http://www.w3.org/TR/html5/strict.dtd">
A<!DOCTYPE html>
B<!DOCTYPE HTML5>
C<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 5.0//EN"
D"http://www.w3.org/TR/html5/strict.dtd">