Which of the following is a difference between the straight$-$line method and the double$-$declining$-$balance method of depreciation?

a$.$ The straight$-$line method depreciates an asset below its residual value, whereas the double$-$declining$-$balance method does not depreciate an asset below its residual value.

b$.$ In the straight$-$line method, depreciable cost is calculated as cost less residual value, whereas in the double$-$declining$-$balance method, depreciable cost is recorded as declining book value over the fixed asset's useful life.

c$.$ The straight$-$line method does not require an outlay of cash when depreciation is recorded, whereas in the double$-$declining$-$balance method an outlay of cash is required when depreciation is recorded.

d$.$ According to the straight$-$line method, depreciation declines over an asset's useful life, whereas according to the double$-$declining$-$balance method, depreciation increases over an asset's useful life.