Afriend says, "stars produce energy by a fusion chain reaction of helium into hydrogen." evaluate the validity of this statement. a) it is an valid statement. stars produce energy by a fusion chain reaction of hydrogen into helium. b) it is an invalid statement. stars produce energy by a fusion chain reaction of hydrogen into helium. c) it is an invalid statement. stars produce energy by a fission chain reaction of hydrogen into helium. d) it is an valid statement. stars produce energy by fission and fusion chain reactions of hydrogen into helium and vice versa.