Question

what is the main source of energy that powers a star during most of its life?
○ gravitational contraction
○ radioactive decay
○ nuclear fission
○ nuclear fusion
name: *
your answer
which of the following is a key principle of sustainable development? *
○ focusing exclusively on environmental protection
○ maximizing short - term economic gains
○ prioritizing resource extraction over conservation
○ balancing environmental, economic, and social considerations
which of the following is not a type of tectonic plate boundary? *
○ convergent boundary
○ subduction boundary
○ divergent boundary

Explanation:

First Question (Star Energy Source)

To determine the main energy source of a star during most of its life, we analyze the options:

• Gravitational contraction: Powers a star during its formation (protostar phase), not most of its life.
• Radioactive decay: Not the primary energy source for stars.
• Nuclear fission: Involves splitting heavy nuclei; stars primarily fuse light nuclei.
• Nuclear fusion: In stars, hydrogen fuses into helium (and later heavier elements in some stages) in the core, producing energy that powers the star for most of its lifespan (main sequence phase).

Sustainable development aims to balance environmental, economic, and social needs. Analyzing the options:

• Focusing exclusively on environmental protection: Ignores economic and social aspects, so not a key principle.
• Maximizing short - term economic gains: Unsustainable as it neglects long - term environmental and social impacts.
• Prioritizing resource extraction over conservation: Contradicts sustainable use of resources.
• Balancing environmental, economic, and social considerations: Aligns with the definition of sustainable development.

Tectonic plate boundaries are of three main types:

• Convergent boundary: Plates move towards each other (e.g., subduction zones, mountain - building).
• Divergent boundary: Plates move apart (e.g., mid - ocean ridges).
• Transform boundary (not listed here, but among the given options): Subduction boundary is a type of convergent boundary (where one plate subducts under another), while convergent, divergent are distinct types. Wait, the options given are Convergent, Subduction, Divergent. Wait, subduction boundary is a subset of convergent boundaries. The question asks which is NOT a type. Wait, the three main types are convergent, divergent, and transform. Subduction is a process at convergent boundaries. So among the given options, subduction boundary is not a distinct type of plate boundary (it's a process at convergent boundaries), while convergent and divergent are distinct types. Wait, maybe the options have a typo, but based on standard tectonic plate boundary types (convergent, divergent, transform), subduction boundary is not a main type (it's part of convergent).

Answer:

D. Nuclear fusion

Second Question (Sustainable Development Principle)