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Question

enter image description here如何在B下方并保持A垂直居中的情况下增加一行？谢谢！

\begin{table}[!t]
\centering 
\caption{Relation of the objectives of this thesis (1, 2, 3 and 4) with the known facts and open questions described in Sections \ref{sec:in-situ}-\ref{sec:veils}.}
\label{table:objectives}
\begin{tabularx}{\textwidth}{@{}XXc@{}}
    \toprule
    \multicolumn{1}{c}{Known facts} & \multicolumn{1}{c}{Open questions} & Objectives \\ \midrule
    The resistance to matrix cracking depends on ply-thickness (also known as in-situ effect) & There is no evidence of the in-situ effect under out-of-plane shear & \multirow{10}{*}{1} \\
    &  There is controversy about which damage mechanism triggers the other  &  \\
    Impact failure involves  shear cracks and delaminations & There is controversy about which damage  mechanism   penalizes  the  load-carrying capacity &  \\
    & There is no clear evidence of how ply-thickness affects the damage sequence &  \\ \midrule
    Thin-plies increase certain in-plane mechanical properties  because of the in-situ effect & \multirow{4}{=}{There is little information on how ply-thickness affects thin laminates' impact response} & \multirow{4}{*}{2} \\
    Thin-plies display brittle failure mechanisms &  &  \\ \midrule
    A & Few studies connect the microstructure and the  properties of interleaved systems & \multirow{5}{*}{3$\&$4} \\
    A & B &  \\ \bottomrule
\end{tabularx}%

\ end {table}