您好，我正在从 MiKTeX 运行 TexWorks 并不断收到此错误：
! Undefined control sequence.
l.6 \documentclass
[prd,12pt,reprint,showkeys,showpacs,nofootinbib]{revtex4-1}
?
以下是我的整个序言：
\documentclass[prd,12pt,reprint,showkeys,showpacs,nofootinbib]{revtex4-1}
%additional macros
\usepackage{amsmath} % for creating subequations
\usepackage{graphicx} % for insterting figures
\usepackage{verbatim} % for including verbatim text
\usepackage{color} % for colored text
\usepackage{subfigure} % for side-by-side figures
\usepackage{hyperref} % for creating hypertext links