Final answer:
Blocking, control, randomization, and replication are all required in an experimental design. Therefore correct option is E
Step-by-step explanation:
In an experimental design, blocking, control, randomization, and replication are all required.
Blocking is a technique used to group similar experimental units together to reduce variation.
Control refers to the use of a control group that does not receive the treatment being tested, allowing for comparison.
Randomization is necessary to assign participants randomly to different treatment groups, minimizing bias.
Replication involves repeating the experiment with a larger sample size to ensure reliability.
Therefore, the correct answer is E) All are required in an experimental design.