To answer this question, we need to understand the relationships and marriages mentioned in the given options.
Option A) Ganga and Amba - This option is incorrect because Ganga was the wife of King Shantanu, but Amba was not his wife.
Option B) Ambika and Ambalika - This option is incorrect because although Ambika and Ambalika were the wives of King Vichitravirya (son of Shantanu), they were not the wives of Shantanu himself.
Option C) Ganga and Satyavathi - This option is correct because Ganga and Satyavathi were the wives of King Shantanu. Ganga was the first wife, and Satyavathi was the second wife.
Option D) Devayani and Indra - This option is incorrect because Devayani was not one of the wives of King Shantanu. Also, Indra was a deity and not a wife.
Therefore, the correct answer is option C) Ganga and Satyavathi.