What is the structural formula of 2-bromo-3-chloro-4,4-dimethylpentan al

The structure of the compound is shown in the  image attached to this answer.

We have to remember that the whole idea of IUPAC nomenclature is to create a generally accepted system of chemical nomenclature such that the structure of a compound can be drawn from its name.

From the name 2-bromo-3-chloro-4,4-dimethylpentanal, we can see that the alkanal moiety should occupy position 1. Counting from that position, the bromime is the next substituent (position 2). The chlorine follows (position 3) and the two methyl groups (position 4) as shown in the image attached.

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c is the answer because when something is left after something evaporates that shows the chemical change.