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

1. A

   Activity of radio- active substance - Curie

   Option (a) claims that the activity of a radioactive substance is measured in Curie. While Curie is a traditional unit used to measure radioactive decay, the official S.I. unit for the activity of a radioactive substance is the Becquerel, making this pair incorrectly matched and thus the correct choice for this question.

2. B

   Power of lense - Diopter

   Option (b) states that the power of a lens is measured in Diopter. This is a correctly matched pair because the SI unit of lens power is indeed the diopter, defined as the reciprocal of the focal length in meters.

3. C

   Heat - Joule

   Option (c) claims that heat is measured in Joule. This is a correctly matched pair as heat is a form of energy and its standard International System of Units measurement is the joule.

4. D

   Pressure - Pascal

   Option (d) states that pressure is measured in Pascal. This is a correctly matched pair because pressure is defined as force per unit area, and its standard SI unit is the pascal.

Summary. Official key is (a) because the Curie is an older, traditional unit of radioactivity, whereas the S.I. unit is the Becquerel. The other options correctly pair physical quantities with their standard International System of Units measurements. Diopter correctly measures lens power, joule measures heat energy, and pascal measures pressure. Candidates often confuse traditional legacy units with official S.I. units in physics questions. Therefore, option (a) is the only incorrectly matched pair among the given choices.