Which of the Following Studies Would Shed Light on the Mechanism

Which of the following studies would shed light on the mechanism of spread of H5N1 from Asia to North America?

A) Perform cloacal or saliva smears of migrating waterfowl to monitor whether any infected birds show up in Alaska.
B) Test fecal samples for H5N1 in Asian pet birds that live near domestic poultry farms in Asia.
C) Locate and destroy birds infected with H5N1 in Asian open-air poultry markets.
D) Record the incidence of H5N1 in domestic poultry farms in Asia.