Which code segment should you insert at line 16?

You are developing a C# application. The application includes the following code segment, (Line
numbers are included for reference only.)

The application fails at line 17 with the following error message: “An item with the same key has
already been added.”
You need to resolve the error.
Which code segment should you insert at line 16?

A.
Option A

B.
Option B

C.
Option C

D.
Option D