I am querying
mobile in stackoverflow. The second result is an answer. Results of /search/advanced is giving only questions when queried
mobile. This is applicable for all other terms which are to be queried.
From the docs:
Searches a site for any questions which fit the given criteria.
The searches on the API aren't guaranteed to exactly replicate the current on-site search, so this behaviour is expected. This may change in some future release of the API, but the current behaviour is closer to the old on-site search approach, which only ever returned questions as top-level results.