Answer: The correct answer is d.) None of the above sentences are written correctly.
Explanation: All three options contain grammatical errors or lack clarity in their expression.
a.) The phrase "because she is turning 7" is correct grammatically, but it lacks a necessary punctuation mark. It should be written as "because she is turning 7."
b.) The word "cause" is an informal abbreviation of "because," and it is not appropriate to use in a formal sentence. It should be written as "because" instead.
c.) The conjunction "and" is not used correctly in this sentence. It should be "is turning 7" instead of "and is 7" to indicate the age of the daughter.
Therefore, none of the above sentences are written correctly.