Explanation

Bones do not secrete hormones, which are produced by glands in the endocrine system.

The parathyroid gland secretes parathyroid hormone.

It regulates calcium levels in the blood and bones.

Explanation

Explanation

Biogas is produced under anaerobic conditions; the process is denominated as anaerobic digestion.

The major constituent of biogas is methane (55-70%), CO2 (30-45%) and some traces of gases such as H2S and ammonia.

Explanation

Explanation

Measles is one of the world's most contagious diseases

It spread by contact with infected nasal or throat secretions (coughing or sneezing) or breathing the air that was breathed by someone with measles.

The virus remains active and contagious in the air or on infected surfaces for up to two hours.

Explanation

Due to biomagnification, DDT (Dichlorodiphenyltrichloroethane) accumulates more in organisms higher up the food chain. 

Seagulls, being top predators, experience the highest deposition of DDT.

Explanation

Explanation

Magnetic property: Thorium is a ferromagnetic metal, meaning it is capable of being magnetized.

Radioactive property: Thorium is also a radioactive metal, emitting alpha, beta, and gamma radiation due to its unstable atomic nucleus.

Explanation

A gene is a segment of DNA that carries the genetic instructions used in the growth, development, and reproduction of organisms.

It is the fundamental unit of heredity.

Explanation

The lungs are the primary organs for gas exchange, where oxygen is absorbed into the blood, and carbon dioxide is expelled.

This process occurs in the alveoli, tiny air sacs in the lungs.