The correct answer is D. Vertical filing.
Vertical filing is a method of organizing paper documents in a filing cabinet. The documents are placed in folders, which are then placed in file drawers. The file drawers are arranged vertically in the filing cabinet.
Vertical filing is the most efficient method of filing for a large undertaking because it allows for easy access to the documents. The documents are stored in a logical order, and they can be quickly retrieved when needed.
Pigeon hole system is a method of organizing paper documents by placing them in slots or holes in a wall or other surface. The slots are typically labeled with the type of document that should be placed in them.
Spike files are a type of file that is used to store paper documents that are not frequently accessed. The documents are placed on a spike that is attached to a stand or wall.
Box files are a type of file that is used to store paper documents that are not frequently accessed. The documents are placed in boxes that are then stored in a closet or other storage area.
Vertical filing is the most efficient method of filing for a large undertaking because it allows for easy access to the documents. The documents are stored in a logical order, and they can be quickly retrieved when needed.