Which of the following transactions or events is treated as a Sec. 1231 gain or loss? All

Question:

Which of the following transactions or events is treated as a Sec. 1231 gain or loss? All assets are held for more than one year.
a. Theft of uninsured diamond ring, with an $800 basis and a $1,000 FMV.
b. Gain due to condemnation of land used in business.
c. Loss on the sale of a warehouse.
d. Gain of $4,000 on the sale of equipment. Depreciation deductions allowed amount to $10,000.