I need help with economics please?

[James Stewart]

8) Costs increase as output increases in an increasing-cost industry because
a)management has less ability to closely supervise work
b)input prices rise
c)machinery becomes less efficient
d)workers become less efficient

9) for a firm in pupre competition, the firm's short-run supply curve is
a)average cost curve above maginal cost
b)marginal cost curve above average cost
c)marginal cost curve above average variable cost
d) average cost curve above average variable cost

10)A firm's supply curve for a firm in pure competition is taken from its
a)average cost curve
b) marginal cost curve
c)total cost curve
d)total variable cost curve