If a cell is like a city, then city hall, or the control center, would be the cell's a) membrane. b) mitochondria. c) nucleus. d) ribosomes.

b. the carbon cycle ensures living things have a source of hydrogen

nucleic acid molecules are incredibly complex, containing the code that guarantees the four different nucleotide units comprise dna, the nucleic acid of interest to the genealogist. and one of four nitrogen-containing molecules called nucleotides