Given a scientific passage and an answer, generate a question for the given answer.

[Q]: Passage: Although most of a cell's DNA is contained in the cell nucleus, mitochondria have their own DNA. Mitochondria also have the machinery to manufacture their own RNAs and proteins. The human mitochondrial DNA sequence has 16,569 base pairs encoding 37 total genes: 22 tRNA genes, 2 rRNA genes, and 13 peptide genes. The 13 mitochondrial peptides in humans are integrated into the inner mitochondrial membrane, along with proteins encoded by nuclear genes. Answer: nucleus
[A]: Where is most of the cell's dna contained?

[Q]: Passage: Carbon has four valence electrons, so it can achieve a full outer energy level by forming four covalent bonds. When it bonds only with hydrogen, it forms compounds called hydrocarbons. Answer: four
[A]: How many valence electrons does carbon have?

[Q]: Passage: Antibodies These proteins recognize and combine with harmful materials, including both toxic chemicals and invasive microorganisms (such as bacteria and viruses). When an antibody binds to its target, it is tagged for destruction. This tag is recognized by white blood cells, which complete the process. Some antibodies also partially or completely deactivate their targets while waiting for further help from white blood cells. Answer: antibodies
[A]:
Which proteins recognize and combine with harmful materials, including both toxic chemicals and invasive microorganisms?