Explanation:

- I. The State Department unveiled a new program to ____ Russian meddling in the 2018 U.S. mid-term elections: This requires a word indicating action against or neutralizing interference.

- II. There was nobody behind the ____ when I went into the bank, and I had to wait to be served: This needs a word representing a physical structure where transactions occur in a bank.

- Option 1: Oppose: Suitable for sentence I, but not for sentence II.

- Option 2: Counter: This word means to act against interference in sentence I and denotes the physical structure in a bank for sentence II.

- Option 3: Shelf: This refers to a place to put items but doesn't fit the context of sentence I or II.

- Option 4: Tackle: Suitable for sentence I, but not applicable for sentence II.