These are words are relative pronouns, but can they ever be used in a question as an interrogative pronoun? I assume that function is reserved for Cuál and Cuáles without el-lo-la-las.
Next, could "cuáles" be used in this quiz sentence: Voy a preguntar a la dependienta ________ lavadoras son más eficientes. trying to ask: which ones of these washing machines are more efficient?