As she failed to produce - heir the queen stood - chance of keeping the throne. A) an/no B) the / most C) a /hardly any D ) some/any E a/none

E) a/none<br /><br />The correct answer is E) a/none. In this sentence, "a" is used before "heir" because it refers to one specific individual, and "none" is used to indicate that there is no chance of keeping the throne.