a) There _____ a man, a lady and some children in the park.
The blank should be filled with is or are ???
In some grammar books, I've read the following sentences:
b) There's a chair and a table in the room.
c) There's a chair and two tables in the room.
d) There are two tables and a chair in the room.
I don't have any doubt on d) but as to a),b),c)
Please,could YOU explain the rule from a point of strictly grammatical view
and in terms of formality?