138. The smallest size of a simple connected graph of order 7 whose largest degree of vertices is 3, is which of the following? (1) $5$ (2) $6$ (3) $7$ (4) $8$
\textbf{138.} The smallest size of a simple connected graph of order 7 whose largest degree of vertices is 3, is which of the following?
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(1) $5$ \hfill (2) $6$ \hfill (3) $7$ \hfill (4) $8$
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