4)
Scientists routinely explore whether two different animal species have evolved from a recent common ancestor. is the LEAST useful technique to help with this determination

Scientists routinely explore whether two different animal species have evolved from a recent common ancestor.Comparisons of items eaten for food is the LEAST useful technique to help with this determination

The features that are related to the anatomy of two organisms when they share them in common indicates that they are evolved from the common ancestor. When there exists a common feature between any two species physically then it is inherited form the common ancestor.

The two species having common traits involves similar genetic material called DNA, genetic codes that are similar and same translation and transcription process. Thus studying about genes and gene expression will be helpful to explore whether  two different animal species have evolved from a recent common ancestor than including the studies related to Comparisons of items eaten for food.

i am positive it is c. condensing but i may be wrong