Step 1: Two factors
Dispersion strength depends on polarisability (more electrons, more polarisable) and shape (more surface contact means stronger attraction).
Step 2: Eliminate
Methane and ethane have far fewer electrons than a five-carbon alkane, so they are weaker.
Step 3: Choose between the isomers
Both pentanes have the same electrons. The linear n-pentane packs side by side with a large contact area, whereas branching makes neopentane compact and reduces the contact.
Step 4: Evidence
Boiling points: n-pentane 309 K, neopentane 283 K. The higher boiling point matches stronger forces in n-pentane.
Final Answer:
n-Pentane has the strongest dispersion forces. This is option (C).
\[ \boxed{\text{(C) }\text{n-Pentane}} \]