Option 1 states that magnification is calculated by dividing the actual size of the specimen by the observed size. This is incorrect. The actual size of the specimen is not divided by the observed size.
Option 2 is the correct answer. It states that magnification is calculated by dividing the observed size of the specimen by the actual size. This is correct. Magnification is the ratio of how much larger an object appears compared to its actual size.
Option 3 states that magnification is calculated by subtracting the observed size from the actual size of the specimen. This is incorrect. Magnification is calculated by division, not subtraction.
Option 4 states that magnification is calculated by subtracting the observed size from the actual Mee (which is unclear) of the specimen. This is also incorrect. Again, magnification is calculated by division.
In conclusion, the correct answer is option 2, where magnification is calculated by dividing the observed size of the specimen by the actual size.