Stronx Consulting Tests Its Salespeople on Listening Skills and Then

Stronx Consulting tests its salespeople on listening skills and then implements a training program to teach all of them to be better listeners.At the conclusion of the last training session,it conducts a posttest to measure listening skills again.Based on the results,the training manager reports that the training program increased listening skills by a significant amount.Which of the following statements represents the main weakness in the manager's conclusion?

A) The actual impact of the training can only be evaluated by comparing the performance of employees who underwent training and those who did not.
B) The posttest evaluated employees for the same levels of knowledge,skill,and competency as the pretest did.
C) Posttests and pretests are very complex,and Stronx Consulting should have used a simpler form of evaluation.
D) The duration of the training was three days,which is comparatively short when compared with the duration of many other training programs.
E) The posttest was conducted immediately after the training program,which is too soon for accurate measurement of learning.