beamer 中的文本对齐问题

Question

尽管右侧有很多空间，但文本还是左对齐。下面是我的 tex 文件的一部分。还附上了输出幻灯片。

请建议我该如何纠正此问题。谢谢。

\documentclass[slidestop,compress,mathserif]{beamer}
\usepackage[latin1]{inputenc}
\usepackage{verbatim}
\usepackage{graphicx}
\usetheme{Boadilla}
\usecolortheme{beaver} %{beetle}%{crane} 
\usepackage{textpos}
\usepackage{tikz}
\usepackage{biblatex}
\addbibresource{ref.bib}

\title[xyz]{Energy Interactions}
\author[Ramkrishna Sharma]{Ramkrishna Sharma}
\institute[DU]{University of Delhi, INDIA}
\date{September 11, 2014}


\setbeamertemplate{footline}[slide number]
\setbeamertemplate{frametitle}[default][center]         % For centering the Heading

\titlegraphic{
    \includegraphics[width=1.5cm,keepaspectratio]{figure/cern.jpg}\hspace*{3.35cm}~%
    \includegraphics[width=2cm,keepaspectratio]{figure/logo_du.jpeg}\hspace*{2.75cm}~%
    \includegraphics[width=1.5cm,keepaspectratio]{figure/cmsLogo.jpeg}
}

\begin{document}
\renewcommand{\inserttotalframenumber}{\pageref{lastslide}}
\begin{frame}
\titlepage
\end{frame}

\begin{frame}\frametitle{Table of contents}\tableofcontents
\end{frame}

\begin{frame}[shrink=20]\frametitle{Motivation}
\begin{block}{Higgs boson Found!!!}
    \begin{itemize}
    \item Discovery of Higgs boson anounced on 4 July 2012.
    \end{itemize}
\end{block}

\begin{block}{Queries}
    \begin{itemize}
    \item But, now the question about Higgs boson split into two queries\footfullcite{Massironi:2014fma}:
        \begin{itemize}
        \item Is this the only Higgs boson present in Nature?
        \item Is it really doing {\bf the Higgs boson} job?
        \end{itemize}
    \end{itemize}
\end{block}
\begin{block}{Answer: Mainly three roads}
    \begin{itemize}
    \item keep searching for scalar outside of m=125GeV\footfullcite{Chatrchyan:2013yoa},
    \item measure with high precision the properties of the 125GeV boson\footfullcite{CMS:2014ega}, and
    \item measure the electroweak vector boson interactions.
    \end{itemize}
\end{block}

\end{frame}
\end{document}