As written, most likely 1 row and 4 columns: 1x4, selection A.
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My calculator might recognize this as a vector (or a list of 4 elements). It would like double brackets to make it a matrix: [[6,2,8,3]] with 1 row. My math program would treat it as either a 1x4 vector or a 4x1 vector depending on the expression it might get used in.
You need to consult your text or other curriculum material to determine the intended meaning of this expression.