According to the Census of India, 2011, the characteristics of urban agglomeration include:
(A) A continuous urban spread constituting a town and its adjoining outgrowths: This is the definition of an urban agglomeration. Therefore, (A) is correct.
(C) Two or more contiguous towns together with or without outgrowths: This also defines an urban agglomeration, where multiple towns are close together. Hence, (C) is correct.
(B) Urban settlements combined with one rural settlement: This is not a characteristic of urban agglomeration. Therefore, (B) is incorrect.
(D) Urban villages engulfed within a metropolitan area: This is a different concept, not specifically related to urban agglomeration. Hence, (D) is incorrect.
Thus, the correct answer is (A) and (C).