The DNA evidence was gathered from the blood stain on the concrete floor. What is the source of DNA?

The most common source of DNA is blood or soft tissue samples. DNA can be also extracted from semen, saliva, hair roots and even from several skin cells left on the surface of a pint glass after it was touched (these sources of DNA are commonly employed in forensic analysis).

blue

light-years

magnitude

sodium i think the chemical element of atomic number 11, a soft silver-white reactive metal of the alkali metal group.