Which of the following words cannot be formed using the letters of the word DICTIONARY?

The correct option is NOTICE.

To find which word cannot be formed, let us count the available letters in the given word DICTIONARY:
D, I, C, T, I, O, N, A, R, Y

Now, let us examine each option:

1. NOTICE: Contains the letter 'E'. Since the letter 'E' is not present in DICTIONARY, this word cannot be formed.

2. CART: Uses C, A, R, and T, which are all present in DICTIONARY.

3. CITY: Uses C, I, T, and Y, which are all present in DICTIONARY.

4. ACTION: Uses A, C, T, I, O, and N, which are all present in DICTIONARY.

Therefore, NOTICE is the word that cannot be formed using the letters of DICTIONARY.