What are some ways that living things can be classified? What characteristics should we look at when putting living things into groups?

The classification of living things includes 7 levels: kingdom, phylum, classes, order, families, genus, and species. Characteristics such as appearance, reproduction, mobility, and functionality are just a few ways in which living organisms are grouped together. These specialized groups are collectively called the classification of living things.

Hope this helps :)

it has one origin of replication, but it proceeds in two directions - d)

blood enters the heart through two large veins, the inferior and superior vena cava, emptying oxygen-poor blood from the body into the right atrium of the heart. as the ventricle contracts, blood leaves the heart through the pulmonic valve, into the pulmonary artery and to the lungs where it is oxygenated.