%%%------------------------------------------------------------------------------------------------------------

\begin{center}
\begin{tikzpicture}

\tikzstyle{wnode}=[inner sep=0mm,minimum height=1.5em,minimum width=2em]

\begin{scope}[sibling distance=15pt, level distance = 30pt]

\Tree[.\node(n1){{S}};
        [.\node(n2){{NP}};
	        [.\node(n3){{PRN}}; \node(w1){{I}};]
		    ]
	        [.\node(n4){{VP}};
	            [. \node(n5){VBP}; \node(w2){{love}};]
	            [. \node(cw4){NP};
                   [. \node(n6){NNS}; \node(w3){{dogs}};]
                ]
	        ]
        ]
     ]

\node [anchor=north] (label1) at ([xshift=0em,yshift=-4em]w2.south) {(a)句法树};

\end{scope}


\begin{scope}[xshift=1.8in,yshift=0em]

\node [anchor=west,wnode] (w1) at (0,0) {I};
\node [anchor=west,wnode] (w2) at ([xshift=3em,yshift=0em]w1.east) {love};
\node [anchor=west,wnode] (w3) at ([xshift=3em,yshift=0em]w2.east) {dogs};

\node [anchor=north,wnode] (w4) at ([xshift=0em,yshift=-2em]w1.south) {$w_1$};
\node [anchor=north,wnode] (w5) at ([xshift=0em,yshift=-2em]w2.south) {$w_2$};
\node [anchor=north,wnode] (w6) at ([xshift=0em,yshift=-2em]w3.south) {$w_3$};

\node [anchor=north] (label2) at ([xshift=0em,yshift=-1.5em]w5.south) {(b)词序列};

\end{scope}

\begin{scope}[xshift=1.2in,yshift=-1.5in]

\node [anchor=west,wnode] (l1) at (0,0) {S};
\node [anchor=west,wnode] (l2) at ([xshift=1em,yshift=0em]l1.east) {NP};
\node [anchor=west,wnode] (l3) at ([xshift=1em,yshift=0em]l2.east) {PRN};
\node [anchor=west,wnode] (l4) at ([xshift=1em,yshift=0em]l3.east) {VP};
\node [anchor=west,wnode] (l5) at ([xshift=1em,yshift=0em]l4.east) {VBP};
\node [anchor=west,wnode] (l6) at ([xshift=1em,yshift=0em]l5.east) {NP};
\node [anchor=west,wnode] (l7) at ([xshift=1em,yshift=0em]l6.east) {NNS};

\node [anchor=north,wnode] (l8) at ([xshift=0em,yshift=-1em]l1.south) {$l_1$};
\node [anchor=north,wnode] (l9) at ([xshift=0em,yshift=-1em]l2.south) {$l_2$};
\node [anchor=north,wnode] (l10) at ([xshift=0em,yshift=-1em]l3.south) {$l_3$};
\node [anchor=north,wnode] (l11) at ([xshift=0em,yshift=-1em]l4.south) {$l_4$};
\node [anchor=north,wnode] (l12) at ([xshift=0em,yshift=-1em]l5.south) {$l_5$};
\node [anchor=north,wnode] (l13) at ([xshift=0em,yshift=-1em]l6.south) {$l_6$};
\node [anchor=north,wnode] (l14) at ([xshift=0em,yshift=-1em]l7.south) {$l_7$};

\node [anchor=north] (label3) at ([xshift=0em,yshift=-1.5em]l11.south) {(c)句法序列};

\end{scope}


\end{tikzpicture}
\end{center}