Select the option that best expresses the meaning of the given idiom.

Burn the midnight oil

The correct answer is To work or study late into the night.

Explanation:
The idiom "burn the midnight oil" originates from the time before electricity, when people relied on oil lamps to provide light. Staying up past dark to study or complete work required burning lamp oil late into the night.

Let's break down each option to see why this is the best fit:
1. To spend money unnecessarily: This refers to squandering financial resources (e.g., "money to burn"), which is unrelated to late-night work.
2. To wake up early in the morning: This describes early rising (e.g., "rising with the lark"), which is the opposite of staying awake late into the night.
3. To waste time on useless tasks: This implies futile effort or procrastination (e.g., "barking up the wrong tree" or "flogging a dead horse"), not dedicated effort late at night.
4. To work or study late into the night: This directly aligns with the idiom's historical origin and modern figurative definition of putting in extra hours of work or study well past midnight.

Therefore, the option that best expresses the meaning of "burn the midnight oil" is To work or study late into the night.