Step 1: Understanding the Concept
Let the line cut the axes at \((p,0)\) and \((0,q)\). Its equation is \(\dfrac{x}{p}+\dfrac{y}{q}=1\).
Step 2: Midpoint condition
Midpoint \(=\left(\dfrac{p}{2},\dfrac{q}{2}\right)=(a,b)\), so \(p=2a\) and \(q=2b\).
Step 3: Substitute
\(\dfrac{x}{2a}+\dfrac{y}{2b}=1\Rightarrow \dfrac{x}{a}+\dfrac{y}{b}=2\).
Final Answer:
The equation of the line is x/a + y/b = 2.
\[ \boxed{\text{(D) }\dfrac{x}{a}+\dfrac{y}{b}=2} \]