HELPP!! HURRY! Based on DNA’s structure and function, why did Meselson and Stahl choose to grow E. coli in broths of nitrogen isotopes?
A. The bacteria's phosphate groups would be replaced by the nitrogen.
B. The nitrogen would be incorporated into deoxyribose.
C. The nitrogen would influence bonding between base pairs.
D. The nitrogen would be incorporated into the DNA nucleotides.

try using substitution:

x + y - 6 = x - y. (i'm not giving you the exact answer). since 0 = x - y, then sub 0 in the equation with x - y. combine your like terms, and then use inverse operations, and you'll have your answer.

: -)

this age may represent the age of the earth's accretion, of core formation, or of the material from which the earth formed. this dating is based on evidence from radiometric age-dating of meteorite material and is consistent with the radiometric ages of the oldest-known terrestrial and lunar samples.

the answer is cell division : )