\begin{table}
\centering
\begin{tblr}[         %% tabularray outer open
]                     %% tabularray outer close
{                     %% tabularray inner open
colspec={Q[]Q[]Q[]Q[]Q[]},
hline{2}={1-5}{solid, black, 0.05em},
hline{1}={1-5}{solid, black, 0.08em},
hline{10}={1-5}{solid, black, 0.08em},
cell{3-4}{1}={c=5}{},
}                     %% tabularray inner close
Sepal.Length & Sepal.Width & Petal.Length & Petal.Width & Species \\
5.1 & 3.5 & 1.4 & 0.2 & setosa \\
hello & hello & hello & hello & hello \\
world & world & world & world & world \\
4.9 & 3.0 & 1.4 & 0.2 & setosa \\
4.7 & 3.2 & 1.3 & 0.2 & setosa \\
4.6 & 3.1 & 1.5 & 0.2 & setosa \\
5.0 & 3.6 & 1.4 & 0.2 & setosa \\
5.4 & 3.9 & 1.7 & 0.4 & setosa \\
\end{tblr}
\end{table} 
