All of the following will cause a shift in the supply of portable power banks except A

Answer: D. a decrease in the prices of portable power banks.

According to the law of supply, an increase in price will cause an increase in quantity supplied when all else is constant. This is also the case when the price decreases. Therefore, a decrease in the prices of portable power banks will cause a decrease in power banks. This is not a shift in supply rather it is a change in price along the supply curve. The supply will shift to the left (a decrease) when there is a decrease in the number of portable power bank manufacturers and an increase in the cost of producing portable power banks. The supply will shift to the right (an increase) when there is a perminus-unit government subsidy on the production of portable power banks.