Which of the following is a simple sentence?

• A. Although it was raining, we decided to go for a walk.
• B. I went to the store and bought some milk.
• C. I went to the store because I needed some milk.
• D. I went to the store where I bought some milk and met my friend.

• I went to the store and bought some milk.

Please select one of the options to reveal the correct answer.