Ji wants to write an example of a frameshift mutation using this sentence: THE CAT SAW THE RAT. Which sentence best shows a frameshift mutation?

A frameshift happens when a letter is inserted or deleted, changing how the remaining letters are grouped. The original sentence has 15 letters when spaces are removed: THECATSAWTHERAT. Choice D, “THC ATS AWT HER AT,” has one fewer letter, so the groups shift after a letter is deleted. The other choices rearrange or add whole three-letter groups without shifting the reading frame.

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