Topic: Affirmative Negative Agreement,

Best Answer Explained in Below-:

The question utilizes a structure that expresses agreement in negative statements. In the first part, "My friend does not like sweet," the phrase implies a negative sentiment towards sweet flavors. The response, "___ do I," requires a phrase that indicates the speaker also shares this dislike for sweet flavors.

The provided options can be analyzed as follows:

- **A) neither**: This option correctly conveys agreement through negation. "Neither do I" implies that the speaker also does not like sweet, aligning perfectly with the friend's sentiment.

- **B) so as**: This is not a suitable phrase in this context, as it does not effectively communicate a negative agreement.

- **C) either**: Although "either" is often used in contexts of choice or alternatives, it doesn't appropriately fit here because the statement is not about choosing between two options but rather expressing a shared dislike.

- **D) so**: This word typically expresses affirmation or agreement in positive contexts, hence it contradicts the negative sentiment already established.

In summary, "neither" is the only option that accurately reflects the shared negative sentiment, making it the correct answer.