i.
Neither the boys nor he knows the one I referred to.
Correct in AmE, where verbal agreement in the case of an alternative conjunct (NP1
or NP2) is with whichever lies closer to the finite verb (here NP2). Many BrE speakers, however, tend to treat such conjuncts as
additive, resulting in a plural verb-form.
ii.
There are a large number of birds on that tree.
'In' might well be more natural, depending on the position of the birds. 'On' could be interpreted as indicating the very top of the tree, as opposed to the lower branches.
iii.
*Each of the horses rear and threw their riders.
An unacceptable combination of tenses: either 'rear and throw' or 'reared and threw'. In addition, 'each' is a singular pronoun, and 'their riders' should therefore be replaced by 'its rider' (assuming, of course, only one rider per horse!)
iv.
I am very surprised at his succeeding.
Possible, but noun 'success' would be more idiomatic.
v.
He expected to have failed in that subject.
Grammatical, but appropriate only where the act of failing
precedes the conception of the expectation. Where, however, the expectation relates to a
later event, the simple, not perfect, infinitive 'to fail' would of course be required.
vi.
*It is I who is responsible for the cessation of fire.
Ungrammatical. Relative pronouns in formal/careful usage take the person and number of their antecedent, and govern the verb accordingly. The antecedent of 'who' is 'I', a first-, not a third-, person pronoun.
Amend, therefore, to:
It is I who am responsible...
vii.
!Alarmed at the news, the boat was launched at once.
A grammatical but absurd sentence, in which it is asserted that a boat felt 'alarmed'! To avoid this kind of so-called 'dangling participle', the sentence needs to be rephrased, using e.g. an absolute construction, as follows:
The sailors being alarmed at the news,....
viii.
We guarantee to fully satisfy all your needs.
Acceptable for the vast majority of contemporary speakers.
A small number of users, however, who hold to the interesting view that English syntax should be based on that of Latin, and that an infinitive should never be separated by anything from the 'to' that precedes it, will tend to maintain vehemently that it should read
We guarantee fully to satisfy all your needs.
I would suggest ignoring them. (Unless, of course, you believe that English nouns ought to be declined in 6 cases and that all English verbs should have a supine!
)