Which code segment should you insert at line 06?

You are developing an application that will convert data into multiple output formats.
The application includes the following code. (Line numbers are included for reference only.)

You are developing a code segment that will produce tab-delimited output. All output routines
implement the following interface:

You need to minimize the completion time of the GetOutput() method.
Which code segment should you insert at line 06?

A.
Option A

B.
Option B

C.
Option C

D.
Option D

Explanation:
A String object concatenation operation always creates a new object from the existing string and the
new data.
A StringBuilder object maintains a buffer to accommodate the concatenation of new data. New data
is appended to the buffer if room is available; otherwise, a new, larger buffer is allocated, data from
the original buffer is copied to the new buffer, and the new data is then appended to the new buffer.
The performance of a concatenation operation for a String or StringBuilder object depends on the
frequency of memory allocations. A String concatenation operation always allocates memory,
whereas a StringBuilder concatenation operation allocates memory only if the StringBuilder object
buffer is too small to accommodate the new data. Use the String class if you are concatenating a
fixed number of String objects. In that case, the compiler may even combine individual
concatenation operations into a single operation. Use a StringBuilder object if you are concatenating
an arbitrary number of strings; for example, if you’re using a loop to concatenate a random number
of strings of user input.
http://msdn.microsoft.com/en-us/library/system.text.stringbuilder(v=vs.110).aspx