Which one of the following would be the most reasonable method of calculating how much energy a bird would require for a migration?

A) Tracking a bird for the duration of the migratory path and estimating its energy usage over that distance
B) Using a wind tunnel to measure metabolic rate at various flight speeds, then using that information to estimate energy usage during the migration
C) Measuring resting metabolic rate in a lab setting and calculating its exercise rate to estimate total usage during the migration
D) Measuring oxygen consumption with some sort of implanted device that the bird carries for the duration of the migration