Final answer:
The action that would decrease the amount of cash on a company's balance sheet is the repurchase of common stock, as it requires spending cash to buy back shares.
Step-by-step explanation:
The action that would decrease the amount of cash on a company's balance sheet, when all other things are held constant, is b) The company repurchases common stock. When a company repurchases its own stock, it uses cash to buy back shares from investors, which decreases the cash balance on its balance sheet. Issuing common equity or preferred stock would increase cash as these actions involve receiving funds from investors in exchange for ownership stakes in the corporation. Increasing accounts payable means the company takes longer to pay its bills, conserving cash, and reducing accounts receivables involves collecting cash from customers, which would also increase the cash balance.