For how many of the following do interfaces exist for implementing direct native client-server protocol? Java, PHP, Ruby

Answer: Option D

This question asks about direct connections between programming languages and a MySQL database.

A direct connection means the language can talk directly to the MySQL server without any intermediaries.

Let's look at each language:

Java has a direct connection interface called JDBC (Java Database Connectivity).

PHP also has a direct connection interface called MySQLi (MySQL Improved).

Ruby has a direct connection interface called mysql2.

Since all three languages have direct connection interfaces, the answer is Option D: 3.