The one that is more restrictive is . . . . . . . .

mysql_query(), mysql_real_query()

This question is about two MySQL functions: mysql_query() and mysql_real_query(). They both execute queries, but there's a key difference in how they handle things.
mysql_query() is a bit more flexible. It can handle both queries and prepared statements. Think of it like a general-purpose tool.
mysql_real_query() is stricter. It's designed specifically for working with prepared statements. It's like a specialized tool for a particular job.
Since mysql_real_query() focuses only on prepared statements, it's considered more restrictive.
So the answer is Option B: mysql_real_query()