3-tier dataflow/communication

hello,

i try to learn the 3tier-architecture
But there are a few question:

1.How can i fill a datagridview in my UI.
the grid should be filled by a dataset.
user can change the data in the grid.
How could this be realized ?
a) The DAL returns a dataset to the BAL and the BAL forwards the dataset to the UI?
b) The DAL returns a datatable to the BAL and the BAL creates a dataset and forwards it to the UI?
c) other?

2.How can i update the database ?
That should be realized with the DataAdapter, right?

bye jogi