a) Continuous refiners
b) Continuous disks
c) Continuous sheets
d) Continuous templates

Answer: a
Explanation: In many paper mills, beaters have been replaced by continuous refiners, such as disk refiners (where rotary disks rotate against a working surface) and conical refiners. However, the batch beater is a convenient vessel for adding chemicals and mixing them intimately with the pulp in order to give special properties to the final paper.