To prevent the accumulation of unnecessary filing, a regular follow$-$up system will make the clearing of files a continuous process. The

removal of outdated papers must be a regular duty in any filing operation. This statement most nearly means that:

files should be regarded as storage space for only the most used material

under an efficient filing system unused material is not filed

a filing system is not usable without a continuous follow$-$up system

the removal of outdated papers will help prevent the accumulation of unused material