у мну как раз тут студенты задавались этими тремя вопросами, а тут би-би-си прям кстати на все три
на одной странице ответило) Вдрук если ещо кому надо:
1. When can I use ‘If I was…’?
2. Which is correct: ‘there is a number of people’ or ‘there are a number of people’?
3. An hour after 11 a.m., is it 12 a.m. or 12 p.m.?
Ответы)1. If I was… is a colloquial alternative to If I were….
In speech, many English people say If I was…, but If I were… is held to be grammatically correct. It is better, therefore, to stick to If I were…, as in these two examples:
‘If I were you, I’d fill the tank now so that we don’t run out of petrol.’
‘If I were to call in on my way home from work, would that be all right?’
2: Some singular expressions referring to more than one person or thing are commonly used with plural verbs, 'a number of' is one of those expressions.
‘There are a number of people in that room.’
3. It's neither! a.m. means before midday, p.m. means after midday so midday itself is neither a.m. or p.m. To be accurate we can say 12 o'clock midday or 12 noon.