Human Body

In both the Earth's crust and the human body, the element with the highest percentage by weight is oxygen.

The Earth's crust is the outermost layer of the Earth, lying above the mantle. It is a solid, rigid layer that is relatively thin compared to the Earth's other layers, such as the mantle and core. The Earth's crust is made up of a variety of rocks and minerals and plays a crucial role in the structure and functioning of the planet.

The Earth's crust is mainly composed of silicon and oxygen, with common minerals such as feldspar, quartz, mica, and basalt (in oceanic crust) and granite (in continental crust).

• Hydrogen (A): Abundant in the human body (e.g., in water) but not the highest by weight. Minimal in Earth's crust.
• Carbon (B): Essential for organic molecules but ranks lower in weight percentage.
• Oxygen (C): Correct answer—constitutes ~46% of Earth's crust (by weight) and ~65% of the human body (primarily in water and biomolecules).
• Calcium (D): Significant in bones but far less abundant than oxygen.

Thus, the answer is (C) Oxygen.

​The flow of milk during breastfeeding follows this sequence:​

• Alveoli: Milk is produced in the alveoli, which are small, grape-like clusters of cells within the mammary glands.​
• Mammary Tubules: The milk from the alveoli drains into the mammary tubules.​
• Mammary Ducts: These tubules converge into larger mammary ducts, which transport the milk towards the nipple.​
• Mammary Ampulla (Lactiferous Sinus): Before reaching the nipple, the milk enters the mammary ampulla, also known as the lactiferous sinus. This area serves as a reservoir where milk can collect.​
• Lactiferous Ducts: Finally, the milk is expelled through the lactiferous ducts that open at the nipple, allowing the infant to feed.​

Therefore, the correct path of milk flow during breastfeeding is:​
(D): Alveoli → Mammary Tubules → Mammary Ducts → Mammary Ampulla → Lactiferous Ducts

This sequence ensures the efficient production, storage, and delivery of milk to the nursing infant.