what is the difference between a food chain and a food web?

a. a food chain shows a direct relationship; a food web shows a complex relationship.
b. food chains only occur in upper-latitude climates; food webs only occur in mid-latitude climates.
c. food chains happen prior to photosynthesis; food webs occur post photosynthesis.
d. a food chain create a climax community; a food web sustains that community.