DNA Pairing =, not understood


I am facing an issue understanding this test.

Best Regards

function pairElement(str) {
return str;

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Challenge: DNA Pairing

Link to the challenge:

What do you not understand? Reading this, it isn’t well explained at all, but:

C pairs with G
A pairs with T


You have a string, “GCG”.
“G” pairs with “C”
“C” pairs with “G”
“G” pairs with “C”
Output should be [["G", "C"], ["C", "G"], ["G", "C"]]

It’s asking you to split a string into an array, mapping each character to an array with the correct pairing