The market for hand sanitizer was greatly impacted by the Covid pandemic in 2020. We saw a great demand for hand sanitizer but had low supply in the beginning of the pandemic.

The external factor in this example is

A small island community's primary source of food is fishing. The island's fish population has drastically declined due a recent period of unusually warm ocean temperatures.

THERE WOULD BE A(N) _ OF FISH

It's the day after Valentines Day and Target has a ton of heart shaped chocolate boxes left over.
THERE IS A(N) _ OF CHOCOLATE BOXES.

DEMAND deals directly with the

The demand curve slopes down because as the price falls for a product/service consumer will demand more of the product/service.

When price is high, consumers will demand

When price is low, consumers will demand

SUPPLY deals directly with the

Supply curves up because as price increases producers supply less of that product/service.

When price is high, producers will supply

When price is low, producers will supply