1) There isn't ... work to do today. 2) We found ... mushrooms in the forest. 3) How ... chairs are there in this room? 4) ... people can use the Internet nowadays.

1) There isn't much work to do today.

2) We found many mushrooms in the forest.

3) How many chairs are there in this room?

4) Many people can use the Internet nowadays.

Many употребляется с исчисляемыми существительными, much - с неисчисляемыми.

Work - неисчисляемое сущ.;

mushrooms - исчисляемое сущ.;

chairs - исчисляемое сущ.;

people - исчисляемое сущ.