Hi Philip! Your answer is really almost right, it would be "A ella le preocupa la radiación" The explanation is simple: the verb "preopupar" works as "gustar" in Spanish, I mean, it´s the radiation that makes her to be concerned, so "a ella" operate as an indirect complement. It´s clear more or less? If you haven't understood I could try it again, just say it to me :)

Hi, here is just an attempt to make this a little bit clearer from one student to another - I trust that native speakers will comment if they don´t agree: Quite a few Spanish verbs that express emotional reactions (preocupar / preocuparse being an example) will have 2 different types of conjugations: 1) Reflexive form (preocuparse) 2) The "gustar"-form - i.e. requires the use of indirect object pronoun (preocupar) In the examples given in your question it looks these two forms have been mixed up - resulting in neither of them being correct. I believe you can express the meaning "She is concerned about the radiation" by choosing one of the following: 1) Reflexive form: "(Ella) se preocupa por la radiación." (Lit.: "She worries herself about the radiation") 2) The "gustar"-form: "(A ella) le preocupa la radiación." (Lit.: The radiation worries her) In order to say "Don´t worry" (imperative), you would only use the reflexive form: "No te preocupes" Hope this helps :)