Step 1: Recall the two basic rules.
For series resistors, \[ R_{eq} = R_1 + R_2 + \dots \] and the current stays the same everywhere. For parallel resistors, \[ \frac{1}{R_{eq}} = \frac{1}{R_1} + \frac{1}{R_2} + \dots \] and it is the current that splits up among the branches.
Step 2: Test option A.
Option A says the series equivalent resistance is the sum of the individual resistances, which is exactly the series rule above, so this statement is true and worded precisely as the textbook law.
Step 3: Rule out the rest quickly.
Option B wrongly applies the series addition rule to a parallel circuit. Option C wrongly claims current adds up in series, when really it stays constant throughout a series loop. Since option A is the one statement that matches a standard law of combination word for word, it is the answer being asked for.
\[ \boxed{R_{eq} = R_1 + R_2 + \dots + R_n \text{ for a series combination}} \]