(what can best be inferred about the hind leg bones seen in whales?
the hind leg bones of the whales are fossil structures from an extinct
ancesot
the hind leg bones of the whales are analogous structures to the fins of
living fish
the hind leg bones of the whales are homologous structures to the wings
of butterflies
d)
the hind leg bones of the whales are vestigial structures that had a
function in an extinct ancestor.

The correct option is D) The hind leg bones of the whales are vestigial structures that had a  function in an extinct ancestor.

Explanation:

Vestigial structures can be described as structures or features which were once useful to the ancestor of a species but currently perform no function in the body of the organism. For example, the appendix of humans.

The hind leg bones of the whales determine that their ancestor might possess these bones for walking purposes. But as the current whales do not walk, hence these structures are vestigial for the current whales.

the electromagnetic spectrum includes, from longest wavelength to shortest: radio waves, microwaves, infrared, optical, ultraviolet, x-rays, and gamma-rays.

i think it would be b. tissue because an organ system is a group of organs that work together to perform one or more functions. each does a particular job in the body, and is made up of certain tissues.