Which sentence in the paragraph conveys the main idea of the letter?

Thank you for opening an account at our bank. We appreciate your interest in our work process. Our employees are friendlier than employees of other banks because we have more time to devote to each customer. Other banks may have as many as 10,000 checking accounts. Their employees are kept busy with procedures. Attending to customers is our employees’ top priority. Please note that other banks close well before 7 p. m.

A.
Our employees are friendlier than employees of other banks because we have more time to devote to each customer.
B.
Thank you for opening an account at our bank.
C.
We appreciate your interest in our work process.
D.
Please note that other banks close well before 7 p. m.