Here's why:
* Infinitives: Infinitives are the base form of a verb, usually preceded by "to" (e.g., "to run," "to sing," "to be"). They are not verbs on their own and don't act as linking verbs.
* Linking verbs: Linking verbs connect the subject of a sentence to a noun or adjective that renames or describes the subject. They are not usually accompanied by an infinitive.
Common linking verbs include:
* Be verbs: am, is, are, was, were, being, been
* Other linking verbs: appear, become, feel, grow, look, remain, seem, smell, sound, taste, turn
Example:
* Correct: "The sky is blue." ("is" is a linking verb connecting "sky" to the adjective "blue.")
* Incorrect: "The sky to be blue." (This uses an infinitive and doesn't make grammatical sense.)
Let me know if you have any more questions!