Ardvark Inc. uses straight$-$line method for financial accounting depreciation and MACRS for tax cost$-$recovery. If tax depreciation is less than book depreciation in the current tax year, what is the nature of the book$-$tax difference associated with these differing methods of depreciation?

$$ A$.$ Permanent; favorable

$$ B$.$ Permanent; unfavorable

$$ C$.$ Temporary; favorable

D$.$ Temporary: unfavorable