Three resistors connected in series have individual voltages labeled V1, V2 and V3, respectively. Which of the following expresses the value of the total voltage VT taken over the three resistors together?

In a series circuit, the total voltage across the entire circuit is the sum of the individual voltage drops across each component. This is a consequence of Kirchhoff's Voltage Law.

Given three resistors in series with individual voltages $\Delta V_1$, $\Delta V_2$, and $\Delta V_3$. The total voltage across these three resistors is $\Delta V_T$.
According to the properties of a series circuit:

Option A matches this relationship.

The final answer is $\text{A. } \Delta V_T = \Delta V_1 + \Delta V_2 + \Delta V_3$.