Step 1: Examine Option (A).
Option (A): “It has wide reach.”
Business letters can be sent across cities, states, and countries through postal services and electronic communication systems.
Thus, they can reach a large audience.
Hence,
\[
{\text{This is an Advantage}}
\]
Step 2: Examine Option (B).
Option (B): “It can be standalone medium.”
A business letter generally contains complete information regarding the matter being communicated. The recipient can understand the message without requiring additional explanation.
Therefore,
\[
{\text{This is an Advantage}}
\]
Step 3: Examine Option (D).
Option (D): “It can be reproduced and repeated.”
Business letters can be photocopied, printed, archived, scanned, and shared with multiple departments whenever required.
Thus,
\[
{\text{This is an Advantage}}
\]
Step 4: Examine Option (C).
Option (C): “It is not cost effective.”
This statement describes a disadvantage rather than an advantage.
In reality, business letters are generally considered economical and cost-effective forms of communication, especially when compared with meetings, travel, or extensive verbal communication.
Therefore,
\[
{\text{This is NOT an Advantage}}
\]
Step 5: Select the correct answer.
Among the given options, only Option (C) represents a disadvantage rather than an advantage.
Hence,
\[
{\text{Option (C)}}
\]
is the correct answer.
Conclusion:
Business letters have wide reach, can function independently as a communication medium, and can be reproduced whenever necessary. The statement “It is not cost effective” does not represent an advantage.
Therefore, the correct answer is:
\[
{\text{Option (C)}}
\]