Given the scenario where the company has 50 private IP addresses but only one public IP address that is not fixed, the NAT conversion method that meets the needs is:

**C. NAPT (Network Address Port Translation)**

Here’s why:

- **NAPT (Network Address Port Translation)**: Also known as PAT (Port Address Translation) or overload, this method allows multiple private IP addresses to share a single public IP address by using different port numbers. This is ideal for situations where you have a limited number of public IP addresses but need to accommodate many internal devices.

- **Static NAT**: This method maps a specific private IP address to a specific public IP address. Since you only have one public IP address and it is not fixed, static NAT is not suitable because it does not handle dynamic or multiple connections efficiently.

- **Basic NAT**: This typically refers to static NAT where one private IP is mapped to one public IP address. It does not support multiple private IPs sharing a single public IP effectively.

- **Easy-IP**: This term might be specific to certain vendors or products, but in general NAT terminology, it does not describe a standard method for handling multiple private addresses with a single public address.

Therefore, **NAPT** is the correct method for translating multiple private IP addresses to a single public IP address, meeting the company’s needs....