What are the costs that do not vary with productions and sales levels called?

of course fixed costs remains same regardless of any production activity...Like Rents, Salaries, Depreciation costs, interests occurred etc...

My answer is just at the No. 1 answer.

A. is the answer, due to the fact that fixed costs have to be paid irrespectively of variations in business activities.

............................. c................................

costs that do not vary with production and sales is called Standerd Cost

variable cost per unit bases does not vary regardless of activity level so in totality the total variable cost varies with activity level. similarly the fixed cost per unit varies with respect to activity level but in totality the Fixed Cost remains same.