If a security officer observes a shopper stealing merchandise and exiting a store, what can the officer arrest the shopper for?

The correct choice is theft because stealing merchandise as a shopper clearly constitutes the unlawful taking of someone else's property with the intent to permanently deprive the owner of it. This action fits the legal definition of theft in California law, which encompasses various forms of stealing, including shoplifting.

Burglary, on the other hand, involves entering a building or structure with the intent to commit a crime inside, which is not applicable in this scenario since the shopper did not enter with criminal intent but rather took the merchandise without paying for it.

Robbery is defined as taking property from a person by force or intimidation, which again does not apply here since the shopper left the store without a confrontation and did not use force. Shoplifting is a specific type of theft that directly pertains to stealing from a retail establishment, but the more general term "theft" is appropriate in a broader legal context. Therefore, in this situation, the term theft captures the essence of the crime committed.