Choose the correct answer from the options given below:

1. (A) – (I), (B) – (II), (C) – (III), (D) – (IV)
2. (A) – (I), (B) – (III), (C) – (II), (D) – (IV)
3. (A) – (I), (B) – (II), (C) – (IV), (D) – (III)
4. (A) – (III), (B) – (IV), (C) – (I), (D) – (II)

   Extremophiles MCQ matching halophile, acidophile, thermophile, and microaerophile with examples is a key topic in microbiology exams. The correct answer is option 4: (A)-(III), (B)-(IV), (C)-(I), (D)-(II).

   Correct Answer

   Option 4: (A) – (III), (B) – (IV), (C) – (I), (D) – (II)

   This matches A-Halophile to Halobacterium (III), B-Acidophile to Sulfolobus (IV), C-Thermophile to Thermus aquaticus (I), and D-Microaerophile to Treponema (II).

   Option Explanations

   Halophile (A) – Salt-loving

   Halobacterium thrives in high-salt environments like salt lakes, requiring 15-30% NaCl.

   Acidophile (B) – Acid-loving

   Sulfolobus grows in acidic hot springs (pH 1-4) at 75-80°C, an archaeon extremophile.

   Thermophile (C) – Heat-loving

   Thermus aquaticus lives in hot springs at 70-80°C, famous for Taq polymerase in PCR.

   Microaerophile (D) – Low oxygen

   Treponema (e.g., syphilis spirochete) prefers 2-10% oxygen, avoiding high levels.

   Options Breakdown

   Option	A-Halophile	B-Acidophile	C-Thermophile	D-Microaerophile	Correct?
   1	I	II	III	IV	No
   2	I	III	II	IV	No
   3	I	II	IV	III	No
   4	III	IV	I	II	Yes

   Extremophile Overview

   Extremophiles adapt to harsh conditions via stable proteins and membranes; archaea like Sulfolobus and Halobacterium dominate.