Which of the following pairs is NOT correctly matched ?
Quantity S. I. Unit

The International System of Units (SI) provides a standardized framework for measuring physical quantities. The analysis of the pairs is as follows:

• Power of lens: Its SI unit is the dioptre (D), which is equivalent to m-1.
• Pressure: The SI unit is the pascal (Pa), defined as one newton per square metre (N/m2).
• Heat: Being a form of energy, its SI unit is the joule (J).
• Activity of a radioactive substance: The SI unit is the becquerel (Bq), which represents one nuclear decay per second. The curie (Ci) is an older, non-SI unit of radioactivity (1 Ci = 3.7 × 1010 Bq).

Since Curie is not the SI unit for radioactive activity, option C is the incorrectly matched pair.