Which of the following statements is correct?

Our body works within the pH range of 7.0 to 7.8.

The correct answer is Option (3)- Our body works within the pH range of 7.0 to 7.8.

Out of the choices you provided, the closest statement to being correct is:  Our body works within the pH range of 7.0 to 7.8.

Let's analyze each statement for accuracy:

• Living organisms can survive a wide range of pH change (Mostly Incorrect): While some organisms can tolerate a wider pH range than others, most organisms have a narrow range within which they can survive. Extremes of pH (very acidic or very basic) can be detrimental or even fatal.
• When pH of rain water is less than 8.2, it is called acid rain (Incorrect): Acid rain is defined as rain having a pH lower than 5.6, not 8.2.
• Our body works within the pH range of 7.0 to 7.8 (Mostly Correct): This statement is closest to being accurate. Our body maintains a strict internal pH balance around 7.4, which is slightly basic. Deviations from this range can cause serious health problems.
• Tooth decay starts when the pH of the mouth is lower than 1.5 (Incorrect): Tooth decay starts when the pH in the mouth drops below a critical level, but it's not as low as 1.5. The threshold is around pH 5.5. At this level, tooth enamel begins to demineralize, creating an environment for cavities to develop.

Therefore, while option 3 isn't entirely perfect (the body's ideal pH is closer to 7.4), it's the most accurate statement compared to the others.