Which of the following most logically completes the argument below?
A non-profit organization is deciding whether to deliver and administer a limited quantity of a new vaccine for malaria, a mosquito-borne disease, to Country A or Country B, two countries with equal populations that are evenly distributed geographically and equally at risk of malaria. The expected rate of success per administration is expected to be the same in each country, but the non-profit organization has limited time to administer the drug and is uncertain of reaching either population in its entirety. Country B is smaller. Therefore, administering the vaccine to Country B will be more effective than administering to Country A, since _______________.