Quickly! multiple answers. more than one choice pls.
why have the gaps among existing organisms as well as the fossil records remained after hundreds of years of research?
1. because insufficient numbers of modern specimens have been examined
2. because distinct populations of living things exist due to barriers to reproductive change
3. because fossils may be classified into distinct taxa due to the persistence of gaps
4. because insufficient numbers of fossil specimens are available

-because distinct populations of living things exist due to barriers to reproductive change.

-because fossils may be classified into distinct taxa due to the persistence of gaps.

The two reasons why the gaps among existing organisms, as well as the fossil records have remained after hundreds of years of research are because of distinct populations of living things exist due to barriers to reproductive change and because fossils may be classified into distinct taxa due to the persistence of gaps.

Option C, because fossils may be classified into distinct taxa due to the persistence of gaps

Option D,  because insufficient numbers of fossil specimens are available

Explanation:

In the classification system, the following issues lead to gap -

a) The species that are able to fill the gap with in a taxonomic classification are not identified yet

b) In case these species have been identified they may not have been placed at a proper position due to the missing links

Recently the gap between the dinosaurs and the  Archaeopteryx has been filled when it has been finally concluded that in between these two species lies the species that have avian adaptations and have emerged step by step over 60 Myr

Hence, option C and D are correct

i believe the answer would be b. hope it : )