The Miller-Urey experiment simulated the primitive Earth's atmosphere. The mixture of gases used in the experiment was: MCQ with Answer and Explanation

Explanation:
The Widal test is a serological agglutination test used to diagnose enteric (typhoid) fever, caused by Salmonella enterica serotype Typhi. It detects the presence of specific antibodies (O and H antigens) in the patient's serum against the O (somatic) and H (flagellar) antigens of the Salmonella typhi bacteria. A significant rise in antibody titer indicates an active or recent infection. It is not used for TB (Mantoux test), malaria (blood smear), or dengue (NS1/IgM).

Explanation:
The human skull consists of 22 bones (8 cranial and 14 facial). The femur (thigh bone) is the longest and strongest bone in the human body. Humans have 12 pairs of ribs; the first 7 are true ribs (direct attachment), next 3 are false ribs (indirect), and last 2 are floating. All statements are anatomically correct.

Explanation:
Arthropoda is the largest phylum, with over a million described species, including insects, arachnids, crustaceans, and myriapods. They are characterized by jointed appendages, chitinous exoskeleton, and segmented bodies. Insects alone represent the majority of animal species. Chordata is comparatively smaller.