Answer:
D. Should Shut Down
Explanation:
A perfect competition firm is at profit maximising equilibrium where : Marginal Revenue [Price] = Marginal Cost .
If MR > MC : Firm's additional production is profitable, it tends to increase production. If MR < MC : Firm's additional production is loss making, it tends to decrease production.
However, If firm's Price i.e MR < Average Variable Cost : The firm's per unit price is even unable to cover it's per unit average variable cost. This situation is referred to as 'Shut Down' point & firm should close down its production in the case.
Given : MR = P = 3 ; MC = 4 ; AVC = 3.5 . The firm's price P (3) is not only lesser by its Marginal Cost MC (4), to decrease production ; but also lesser than its Average Variable Cost AVC (3.5) . So, the firm should shut down.