Question: In ActiveRecord, what is the difference between the `has_many` and `has_many :through` associations?

1. The `has_many: through` association is the one-to-many equivalent to the `belongs_to` one-to-one association.
2. Both associations are identical, and `has_many: through` is maintained only for legacy purposes.
3. The `has_many` association is a one-to-many association, while `has_many: through` is a one-to-one association that matches through a third model.
4. Both are one-to-many associations but with `has_many :through`, the declaring model can associate through a third model.

Answer: The correct answer of the above question is Option D:Both are one-to-many associations but with `has_many :through`, the declaring model can associate through a third model.