In the passage about the quest for a happy life, choose the correct word for the blank: "The quest for a _____ life engrosses every human being on this earth."

Introduction / Context:
This question is part of a cloze passage about the universal human search for happiness. Cloze tests assess vocabulary, reading comprehension, and your ability to detect logically and semantically appropriate words in context. The sentence under consideration reads: "The quest for a _____ life engrosses every human being on this earth." You need to select the adjective that best captures the central theme of the whole passage, which is about happiness, individual definitions of a good life, and philosophical reflections on pleasure.

Given Data / Assumptions:
- The sentence speaks about a "quest", which implies searching or striving for something desired.
- The noun following the blank is "life".
- Later sentences mention "a happy life" being defined in an individualistic way, and the role of hedonists in connecting happiness with physical appetites.
- The options are "simple", "sad", "happy", and "real".

Concept / Approach:
The passage focuses on happiness as the central goal of human beings. The phrase "quest for a happy life" is idiomatic and commonly used in philosophical and everyday discussions. While a simple or real life may also be desirable, the context explicitly later uses the expression "a happy life" and discusses how different people define happiness. Therefore, the blank at the start sets up the theme of the whole passage, and the only choice that aligns perfectly with the rest of the text is "happy".

Step-by-Step Solution:
Step 1: Read the sentence in isolation: "The quest for a _____ life engrosses every human being on this earth." Step 2: Consider "sad". A sad life is not something people actively quest for; this conflicts with the positive sense of "quest". Step 3: Consider "simple". Many people may want a simple life, but the later part of the passage repeatedly uses the term "happy life", not "simple life", as the main theme. Step 4: Consider "real". A real life may sound philosophical, but again it does not match the focus on happiness discussed later. Step 5: Consider "happy". This fits both common usage and the repeated references to happiness in the subsequent sentences.

Verification / Alternative check:
Read the first two lines of the full passage with "happy": "The quest for a happy life engrosses every human being on this earth. Everyman tends to define a happy life in a distinctly individualistic fashion." The repetition of "happy life" in both sentences creates cohesion and makes logical sense. If you insert "simple" or "real" in the first blank, the second line becomes less connected and the central theme becomes unclear.

Why Other Options Are Wrong:
- "simple": Does not link directly with the later philosophical discussion about happiness and hedonism.
- "sad": No one searches for a sad life, so it conflicts with the idea of a quest and with basic human psychology.
- "real": Although interesting, it is not supported by the rest of the passage, which is explicitly about "happy life".

Common Pitfalls:
Some students select "simple" because they associate it with peace and contentment. However, cloze tests require you to consider the wider context. Always read the surrounding sentences; the repeated focus on "happy life" is a clear hint that the first blank should also contain "happy". Memorising frequent collocations such as "quest for a happy life" can also help in similar questions.

Final Answer:
The word that best completes the sentence is happy, giving the phrase "The quest for a happy life engrosses every human being on this earth."