One Word Substitution

Concept: This question asks for a specific term that describes a person based on their belief (or lack thereof) in God or gods. Step 1: Defining the terms in the options
(1) Theist: A person who believes in the existence of a god or gods, especially a creator who intervenes in the universe. (From Greek "theos" meaning god).
(2) Atheist: A person who disbelieves or lacks belief in the existence of God or gods. The prefix "a-" often means "not" or "without". (a-theist: without god).
(3) Religious: Relating to or believing in a religion. While many religions involve belief in God or gods, being religious is a broader term that encompasses practices, rituals, and a system of faith. One could be religious without a traditional theistic belief (e.g., some forms of Buddhism).
(4) Irreligious: Indifferent or hostile to religion, or having no religious beliefs. This is related to religion as a system, not specifically to the belief in God, although there's often overlap with atheism. Step 2: Matching the definition The definition given is "One who does not believe in God". This directly matches the definition of an Atheist.

Step 1: Understand the Definition. The phrase "The act of afforestation by planting many trees" refers to the process of planting trees to create or expand forests. The term that best describes this activity is afforestation. Step 2: Analyze Each Option.
Option (1): Deforestation — Incorrect, as deforestation refers to the removal of forests, which is the opposite of planting trees.
Option (2): Afforestation — Correct, as afforestation specifically means planting trees to create or expand forests.
Option (3): Forest — Incorrect, as "forest" is a noun referring to a large area covered with trees, not the act of planting them.
Option (4): Defrost — Incorrect, as defrosting refers to removing frost or ice, which is unrelated to planting trees. Step 3: Final Answer. $ $