Effect of fseek in a read loop: Given the code that copies from source.txt to target.txt but calls fseek(fs, 4L, SEEK_CUR) after each character read, what will be written to 'target.txt' if the source line is "To err is human"?

Introduction / Context:
This problem tests understanding of file positioning functions in C, specifically how fseek interacts with sequential reading in a loop. By skipping a fixed number of bytes after each successful read, the program samples characters at a specific stride across the source text. Predicting the resulting output requires careful attention to the order of operations and the stride length.

Given Data / Assumptions:

• Source text is exactly: "To err is human" (including spaces, no trailing newline considered).
• The loop reads one character at a time using getc(fs).
• After each non-EOF character, the code executes fseek(fs, 4L, SEEK_CUR) and then writes the character to the output with fputc.
• Files open in text mode; each seek moves the position in bytes across this ASCII text.

Concept / Approach:

• Each iteration reads one byte, then skips forward 4 bytes due to fseek with SEEK_CUR.
• This creates an effective stride of 5 bytes per iteration (1 read + 4 skipped).
• The resulting output is every 5th character of the source, starting from index 0.

Step-by-Step Solution:

Verification / Alternative check:

Why Other Options Are Wrong:

• 'r n': Misinterprets spacing and skip pattern; does not align with the 5-byte stride.
• 'err': Would require reading contiguous indices 2–4 or similar, which the code does not do.
• None of above: Incorrect because 'Trh' is precisely produced by the loop.

Common Pitfalls:

• Forgetting that the seek occurs after the character is read and queued for write.
• Assuming fseek skips characters without considering the initial position and EOF handling.

Final Answer: