one of the pieces of evidence supporting energy quantization was the line spectra of elements. why does this demonstrate energy quantization?

Which supports the idea that birds and butterflies both have wings but they do not have a common ancestor with wings? a. the wings are analogous structures that evolved differently and do not have a similar internal structure. b. the wings are homologous structures that evolved differently and do not have a similar internal structure. c. wings of birds are vestigial structures, but the wing structures of bats are not vestigial. d. wings of bats are vestigial structures, but the wing structures of birds are not vestigial

What material does not melt at any temperature

Areaction is first order with respect to reactant x and second order with respect to reactant y. which statement describes the rate law for this reaction?