The correct sentence is:

"My friend Gökhan has a pet dog."

The verb "has" is used to indicate that someone owns or possesses something. In this case, Gökhan owns a pet dog. The word "a" is used as an indefinite article, indicating that there is one pet dog.

Here are some other ways to express the same meaning:

1. Gökhan is a dog owner.
2. Gökhan owns a dog.
3. Gökhan has a dog as a pet.
4. Gökhan keeps a dog as a pet.

I hope this helps!

The most appropriate way to complete the sentence "My friend Gökhan ..." is to add the word "has" before "a pet dog." The complete sentence would be:

My friend Gökhan has a pet dog.

The word "has" indicates that Gökhan owns or possesses a pet dog. It suggests that Gökhan takes care of the dog and is responsible for its well-being. The phrase "a pet dog" indicates that the dog is a domesticated animal that is kept for companionship or pleasure.

Other ways to complete the sentence include:

1. My friend Gökhan loves a pet dog.
2. My friend Gökhan wants a pet dog.
3. My friend Gökhan is thinking about getting a pet dog.

These options express different relationships between Gökhan and a pet dog. For example, "loves" suggests a strong emotional attachment, "wants" indicates a desire to have a pet dog, and "is thinking about getting" suggests that Gökhan is considering the possibility of getting a pet dog.

However, the most appropriate way to complete the sentence is to add the word "has" before "a pet dog." This option is the most concise and straightforward way to convey the information that Gökhan owns a pet dog.