The best answer is:
A. Bird A survives; either bird B or bird C dies, and the other survives.
Bird A can still find food, as it eats insects and plant seeds, although seeds may be more scarce. Bird C primarily eats plant seeds, which would likely be unavailable due to the drought. Bird B, which relies on nectar from flowers, would also face a lack of food. Thus, either Bird B or Bird C is likely to die due to the loss of their food source.