Which phrase means to refill the gas tank?

• A. Fill up
• B. Fill out
• C. Fill in
• D. Fill

Answer: (A)

Refilling to full capacity uses the phrasal verb that adds up to convey becoming full. To refill the gas tank, you’d say you need to fill up the gas tank. The form with up is the natural collocation for bringing something to its maximum level, especially containers like a tank or a bottle.

Fill out is about completing a form, not adding fuel. Fill in is about supplying missing information or substituting, rather than making something reach full capacity. Fill alone is generic and can mean many things, but it doesn’t specifically emphasize reaching the top or maximum level like fill up does.