In the second step of the mechanism of ozonolysis of alkenes, the ozonide described earlie...

In the second step of the mechanism of ozonolysis of alkenes, the ozonide described earlier undergoes a fragmentation-recombination process to give a 1,2,4-trioxolane.

The fragmentation step is the reverse of a 1,3-dipolar cycloaddition and yields a carbonyl compound and a 1,3-dipolar compound X. The carbonyl compound and X then react to give the 1,2,4-trioxolane by 1,3-dipolar cycloaddition. What is the structure of X?

A.

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B.

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C.

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D.