During the drought of 1977 on daphne major, the best kind of beak for opening tibulous fruit was both deep and narrow. but the evolutionary change that occurred in the population was toward beaks that were, on average, deeper and wider. why?

Please see below.

Explanation:

Some alleles have multiple effects in the phenotype. The allele that causes beaks to be deeper likely also causes the beaks to be wider, so both traits are associated and will vary together. Therefore the population will always show a deeper and wider beak or a shorter and narrower beak depending on the environmental cues available that select for either state.

"d.) carbon dioxide and hydrogen sulfide"