The correct answer is: A. It became full-fledge state.
Himachal Pradesh was a part of Punjab before 1956. In 1956, the States Reorganisation Act was passed, which reorganized the states of India on linguistic lines. As a result of this act, Himachal Pradesh became a full-fledged state.
Option B is incorrect because Himachal Pradesh did not become a Union Territory after the States Reorganisation Act was passed.
Option C is incorrect because Himachal Pradesh did not become only part of Punjab after the States Reorganisation Act was passed.
Option D is incorrect because Himachal Pradesh did not become the part of Jammu and Kashmir after the States Reorganisation Act was passed.