Final answer:
To express D as a function of T and R, we need to know the specific relationship between these variables. Mathematical operations such as addition, subtraction, multiplication, and division can be used to balance equations and define these relationships, similar to balancing a see-saw with equal operations on both sides.
Step-by-step explanation:
To write a rule expressing D as a function of T and R, we must consider the relationship between these variables. The process is similar to balancing an equation, much like a see-saw with equal weights on both sides. For the equation to remain balanced, whatever operation is done to one side must be done to the other.
For instance, in Ohm's Law, if we start with the form V = IR (where V is voltage, I is current, and R is resistance), and we want to express I (current) in terms of V and R, we would divide both sides of the equation by R to get I = V/R. This same balancing act applies to other equations.
Assuming the rule needed is a mathematical relationship between D, T, and R, we would need additional context to determine the precise nature of their connection. Each of the provided options (a through d) represents a different mathematical operation: addition, subtraction, multiplication, and division. The context in which D, T, and R are used will dictate which operation is correct.