Step 1: Understand the meaning of the idiom.
The phrase consists of two important ideas:
• A blessing means something beneficial or fortunate.
• A disguise means something hidden behind a different appearance.
Therefore, the idiom suggests that a beneficial outcome is hidden behind an apparently negative situation.
Step 2: Evaluate Option (A) -- Hidden danger.
A hidden danger refers to something that appears safe but later causes harm.
This meaning is opposite to the idiom.
Therefore, Option (A) is incorrect.
Step 3: Evaluate Option (B) -- A very obvious problem.
An obvious problem is simply a difficulty that is clearly visible.
The idiom refers to an unexpected positive outcome rather than an obvious problem.
Therefore, Option (B) is incorrect.
Step 4: Evaluate Option (C) -- A happy occasion.
A happy occasion is openly joyful from the beginning.
However, the idiom specifically refers to a situation that initially appears bad before revealing its positive side.
Therefore, Option (C) is incorrect.
Step 5: Evaluate Option (D) -- Something that seems bad but turns out to be good.
This option perfectly captures the meaning of the idiom.
A situation may initially seem disappointing, unfortunate, or harmful, but later prove beneficial.
For example:
“Losing that job was a blessing in disguise because it led her to a much better career opportunity.”
Therefore, Option (D) is correct.
Step 6: Determine the correct answer.
The idiom “a blessing in disguise” means:
\[
{\text{Something that seems bad but turns out to be good}}
\]
Hence, the correct answer is Option (D).