Activities of the firm that generates cash is known as"

Sources of cash
Uses of cash
Cash payments
Cash receipts
Cash on hand

If the activity is "generating" cash, is that cash coming in or going out? The answer to that will eliminate some of your choices.

And since the other part of the answer requires knowing the "official" terminology -- I'll just give that one away. We call it sources and uses of cash, not cash receipts and cash payments.

Cash on hand is a balance, which is the net of everything that both came in and went out.