Why have fossil's of some extinct organisms have been found and others haven't?

Ayoung boy has been found and police are trying to locate his family they take a dna sample from him and begin collec dna samples from families who have missing children if police use dna samples only from the fathers, which type of dn technology can they use to identify the boy's parent? y-chromosome analysis omtdna (mitochondrial dna) analysis vntrs (variable tandem repeats) o pcr (polymerase chain reaction) analysis

Which kind of worm has a closed circulatory system? a planarian b fluke c pinworm d an earthworm

As an asteroid comes close to earth, it's name will change to? apex