Birds migrate great distances each year and the primary cue for migration are changes in day length. these changes in day length in turn trigger changes in the birds. behavior and body changes follow as the birds prepare for their seasonal migrations.
a) genetic
b) hormonal
c) physical
d) reproductive

materials water oxygen those are the things i can think of in this moment.

volcanoes (an event in the geosphere) release a large amount of particulate matter into the atmosphere. these particles serve as nuclei for the formation of water droplets (hydrosphere). rainfall (hydrosphere) often increases following an eruption, stimulating plant growth (biosphere).

answer: national resource conservation services

national resource conservation services is the us. based approach that provides technical and financial assistance for natural resource management. nrcs society in conservation of resources by involving in activities like farmland protection, flood prevention, watershed protection, urban conservation, conserves economic and environmental conditions. it conducts soil surveys and implements the policy of natural resources management on the society.