Idioms Phrases

Step 1: Understand idioms.
Idioms are expressions whose meanings are not literal but figurative.
Step 2: Interpret the idiom.
The phrase ``a piece of cake'' is commonly used to describe a task that is very simple or effortless.
Step 3: Analyze the options.
It does not literally mean a dessert, nor does it indicate expense or planning.
Step 4: Conclusion.
Therefore, the correct meaning is something very easy to do.

Step 1: Understand idioms.
Idioms are expressions whose meanings are different from the literal meanings of the words used.
Step 2: Interpret the idiom.
``To burn the midnight oil'' refers to staying awake and working late at night, often for study or work.
Step 3: Analyze the options.
The phrase does not literally mean burning oil or causing trouble.
Step 4: Conclusion.
Hence, the correct meaning is to work late into the night.