Correct Answer: accidental

Solution : The second option is the correct choice.

Intentional means something done with purpose or intent, while accidental refers to something happening by chance or without intent.

The meanings of other options are as follows:

• Voluntary means something that is done willingly or by choice
• Designed means planned or created with a specific purpose in mind
• Calculated means deliberately planned or intended.

Therefore, the correct answer is accidental.