Correct, the two answers b and d are correct!

A shift in phenology can lead to "mismatches" - the peak of caterpillar emergence is no longer at the time of the highest food requirement for rearing young. It is also possible that there is no longer enough food available when the birds need to feed on fat for the migration back to the wintering areas. Migration routes and times have adapted to phenology over thousands of years, so that, for example, the highest abundance of food is found when the most food is needed - during the rearing of young. As climate change causes relatively rapid changes, birds are often unable to adapt.

Source: Both, Visser (2001): Adjustment to climate change is constrained by arrival date in a long-distance migrant bird (Nature)

Xiaohan Li et al 2022 IOP Conf. ser.: Earth Environ. Sci. 1011 012054 at: https://www.researchgate.net/publication/359901817_The_Effects_of_Climate_Change_on_Birds_and_Approaches_to_Response (last accessed on 04.05.2023)