Explanation:

To determine the correct chronological order, we need to recall the years when these states achieved full statehood: - **(C) Nagaland:** Was formed on December $1$, $1963$, as the $16$th state of the Indian Union, carved out of the Naga Hills-Tuensang Area. - **(A) Haryana:** Was created on November $1$, $1966$, as the $17$th state, by bifurcating the erstwhile state of Punjab, based on the recommendations of the Shah Commission. - **(D) Sikkim:** Became the $22$nd state of the Indian Union on May $16$, $1975$, through the $36$th Constitutional Amendment Act, after a referendum. - **(B) Goa:** Achieved full statehood on May $30$, $1987$, becoming the $25$th state of India, separating from the Union Territory of Goa, Daman & Diu. \nArranging these by year, the chronological order is: Nagaland ($1963$), Haryana ($1966$), Sikkim ($1975$), and Goa ($1987$). This sequence corresponds to C, A, D, B. - **Option 1 (A, C, D, B):** Incorrect, as Haryana ($1966$) was formed after Nagaland ($1963$). - **Option 2 (C, A, D, B):** Correct, as it accurately reflects the chronological order of state formation. - **Option 3 (A, D, C, B):** Incorrect, as Haryana ($1966$) was formed after Nagaland ($1963$) and before Sikkim ($1975$). - **Option 4 (C, D, A, B):** Incorrect, as Sikkim ($1975$) was formed after Haryana ($1966$).