I’m a bit confused by the detail in the question of “only one uncle”, because that doesn’t make sense to the question. Assuming it was a mistake and it’s “sister” not “uncle”, the answer is d) You can think of the phrase “who lives in Giza” as an interruption of the phrase “my sister is a journalist”. The commas are what help seperate this from the rest of the sentence. For further explanation, there needs to be a comma after “my sister” because you are talking about “my sister”, not specifically “my sister who lives in Giza” (as that would imply more than one sister). There also needs to be a comma between “who lives in Giza” and “is a journalist” because it is a separation of thoughts. Hope that helped :)

If the question is trying to trick you and the part about the uncle is not a mistake, a) is also grammatically correct