Which of the following sentences is the most formal in style?
A. I want to gain experience with your company, so I'm applying to be an intern.
B. I'm applying to be an intern to gain experience with your company.
C. I'd like to apply for this internship in order to gain experience as a part of your company.
D. I am applying to this internship to gain experience with your company.
The statement used in D is more correct as it explains the connection between the action in the sentence and the resulting outcome.
It also applies expanded form of sentences making it more formal.
Therefore, the Correct Answer is D.