My problem is I don't know what the following 'Infinitive Phrase' functions as:
It is very difficult to explain that clearly. What does 'to explain that clearyly' function as? Please, give me some explanation.
One more thing is about 'Indirect Object':
I pass her a spoon.
I pass a spoon to her.
I know the first 'her' is Indirect object, but I am not sure the second 'her'. In general rule, the preposition 'to' + 'noun or phrase' = a prepositional phrase that functions as an adjective or an adverb. I don't know if 'to' + 'pronoun' = a prepositional phrase functioning as an adjective or adverb. Please, give me clear explanation. Thank you very much for your help.
#1 An appositive phrase renames or describe the preceding word or phrase:
It can be difficult to write clearly.Here's another test. If you move the to-infinitive to the subject position and the resulting sentence is grammatical, you'll know it was appositive phrase:
Question: What can be difficult?
Answer: To write clearly.
It can be difficult to write clearly. <appositive>#2 When the verb's indirect object (e.g., her) takes the form of a prepositional phrase (e.g., to her), it describes where the direct object is moved and so it functions as an adverb:
To write clearly can be difficult. <subject>
Indirect object: I pass her a spoon.
Adverbial phrase: I pass a spoon to her.