Under what conditions are helicopters found to be absolutely essential

A．Because it was very hot the whole night.
B．Because everything is ready for the repairs.
C．Because she had paid a lot for it.
D．Because the maintenance workers are quite efficient.

A．They taste as well as sandwiches do.
B．They are made in a special way.
C．They are not on the menu.
D．They are made by French cooks.