The correct answer is just a bad translation. As given, no one would ever really use the correct answer in every day speech. A house is an inanimate object; it can't "have" anything.
"How many phones are in the house?" is the most natural translation that conveys the main idea of the Spanish sentence. The translation is too literal. Just my opinion though.
I agree with you that "How many phones are in the house?" is the most natural translation. However, even though a house is an inanimate object, even in English, we say that a house has four bedrooms and three bathrooms. Languages are quirky.
How many phones does the house have. Must you say telephones? ?? Phones should be accepted, unless you are being literal
"How many telephones has the house?" Was not accepted by DL. I will try to remember.
there are ??? phones in the house is the common answer anything else is a waste of time and effort
The translation is more than clumbsy; it is wrong. A house can have structures, but cannot have telephones, furniture, appliances, etc.