Begin each interrogative word with a capital letter. Remember to use the prepositions "a" o "de" with the interrogative if one is required. (Lücken)

http://www.colby.edu/~bknelson/SLC/interrogatives3.php

 Begin each interrogative word with a capital letter. Remember to use the prepositions "a" o "de" with the interrogative if one is required. (Lücken)