In grammar, what is the difference between "affect" and "effect"?

The distinction between "affect" and "effect" is fundamental in English grammar, particularly regarding their parts of speech and usage. "Affect" is primarily used as a verb, meaning to influence or make a change in something. For example, one might say, "The weather can affect your mood," indicating that the weather has the power to influence how someone feels.

On the other hand, "effect" is primarily a noun that refers to the result or outcome of a change. For example, one might say, "The effect of the new law was significant," where "effect" describes the impact or result of implementing the law.

Understanding this difference is crucial for using the words accurately in writing and speaking. While some other options mention different parts of speech or suggest they are both verbs or both nouns, these statements do not align with the correct definitions and usages of "affect" as a verb and "effect" as a noun, which is the key reason B is the correct choice.