Select the appropriate meaning of the given idiom.

A hard nut to crack

A difficult problem

The appropriate meaning of the given idiom "a hard nut to crack" is >a difficult problem.<

It means something that is very difficult to understand or solve. The idiom is often used to describe a challenge or obstacle that is difficult to overcome.

The other options are not correct.

• Easily disappointed: This does not mean a difficult problem.
• Not restrained: This does not mean a difficult problem.
• Easily encouraged: This does not mean a difficult problem.