Active, past tense.
The sentence "Humpty Dumpty sat on a wall" is a simple declarative sentence. It states a fact or opinion and expresses a complete thought, consisting of a subject ("Humpty Dumpty") and a predicate ("sat on a wall"). It conveys information in a straightforward manner without any additional clauses or complexity.
In the sentence, You sat down: You is the pronoun subject sat is the verb down is the adverb.
Sat is the verb in that sentence.
The student sat in his desk for the whole class.
There is only one noun in the sentence: student
I sat down.
The first noun in a sentence may be the subject of the sentence, but NOT ALWAYS, for example:John sat on the bench. (the noun 'John' is the subject of the sentence)He sat on the bench. (the pronoun 'he' is the subject of the sentence, the first noun in the sentence is 'bench', the object of the preposition 'on')
Assuming you mean what would the sentence be if all nouns in the sentence The farmer wore the coat and sat on the box by the river were pluralised, then the answer is The farmers wore the coats and sat on the boxes by the rivers
This sentence is a common subject verb object sentence, where the adjective describes the object. In this sentence, the adjective spare describes the desk, telling the reader what kind of desk it is.
Example sentence - Sean and Seth's rickety tree house is being repaired by their uncle.
Sean = Yochanan (×™×•×—× ×Ÿ) which means "God is kind"
I sat in a chair while watching television. Bob slowly sat down, but was still curious!