Step 1: Use the idea of ascribed and achieved status:
Ascribed status comes by birth. Achieved status comes by effort. Caste belongs to the first kind.
Step 2: Test D first:
D says caste is based on abilities and can change. This is the opposite of ascription, so D must be false. Any option with D can be removed.
Step 3: Remove options with D:
Options 2, 3 and 4 all contain D, so they are removed.
Step 4: Check that the remaining option is sound:
Option 1 has A, B and C. A is birth based identity, B is marriage inside the group, C is link with occupation. All three are standard features of caste.
Step 5: Answer:
Only option 1 is left, and it is correct.
Step 6: Quick recap:
A quick memory aid helps here. Remember the three words birth, marriage inside and occupation for caste. Anything that says ability, choice or change over time belongs to class, not caste. This gives A, B and C at once.
Step 7: Final Answer:
Only A, B and C describe caste.
\[ \boxed{\text{Option 1}} \]