$1.$Costs that remain the same in total dollar amount as the activity base changes are called $\_\_\_\_\_\_\_\_.$

a$.$ variable costs

b$.$ fixed costs

c$.$ mixed costs

d$.$ None of these are correct.

abcd

$2.$Costs that vary in proportion to changes in the activity base are called $\_\_\_\_\_.$

a$.$ variable costs

b$.$ fixed costs

c$.$ mixed costs

d$.$ None of these are correct.

abcd

$3.$Costs that have characteristics of both a variable cost and a fixed cost are called $\_\_\_\_\_.$

a$.$ variable costs

b$.$ fixed costs

c$.$ mixed costs

d$.$ None of these are correct.