When Must a Company Generally Elect the Fair Value Option

When must a company generally elect the fair value option for reporting assets?

A) A company can elect the fair value option at any point in the assets life,but can not then revert back to accounting for those assets at cost.
B) A company must typically elect the fair value option at acquisition.
C) A company can typically choose the cost or fair value for each asset each year at the balance sheet date.
D) Companies may not account for assets at fair value.GAAP requires these be recorded at cost.