There is never more than one question in a DNS message

There is always one question in a DNS message; it includes the domain name and the requested datatype and class. There is never more than one question in a DNS message -- the capability of handling more than one would require a redesign of the message format. For one thing, the single authority bit would have to be changed because the answer section could contain a mix of authoritative and nonauthoritative answers. In the present design, setting the authoritative answer bit means that the name server is authoritative for the zone that contains the domain name in the question section.

For you sticklers for detail, there is a time when the number of questions in a DNS message isn't one: in an inverse query, when it's zero. In an inverse query, there is one answer in the query message, and the question section is empty. The name server fills in the question. But, as we said, inverse queries are almost nonexistent.