The structure that separates the thoracic and abdominal cavities is the: MCQ with Answer and Explanation

Explanation:
Codominance occurs when both alleles in a heterozygote are fully and equally expressed. In the ABO blood group system, the IA and IB alleles are codominant. An individual with the genotype IAIB will have both A and B antigens on the surface of their red blood cells, resulting in the AB blood type. It also involves multiple alleles (IA, IB, i).

Explanation:
Enzyme activity depends on pH and temperature; they are not consumed (reusable). Optimum temperature varies; human enzymes around 37°C, but bacterial enzymes can be higher. So 2 is not universally true.

Explanation:
Biochemical Oxygen Demand (BOD) measures the amount of dissolved oxygen required by aerobic bacteria to decompose organic matter in water; high BOD indicates severe organic pollution. Eutrophication is the excessive enrichment of water bodies with nutrients (like nitrates and phosphates), leading to algal blooms and oxygen depletion. Biological magnification is the progressive increase in the concentration of non-biodegradable toxins (like DDT) at each successive trophic level, not a decrease. Thus, statements 1 and 2 are correct.