食いつく

What does 食いつく mean in English?

1. to bite at; to snap at; to nibble(v5k, vi)
2. to get one's teeth into (metaphorically); to get to grips with; to really get into(v5k, vi)
3. to hold on to; to cling to; to stick to(v5k, vi)
4. to complain; to bicker(v5k, vi)