问题
                    
You’ve dropped __________ “s” in the word “across”.-Oh, you are right, __________ letter “s” should be doubled like this “cross”.
                            A:a, a
B:an, a
C:an, the
D:the, a
                        
                        B:an, a
C:an, the
D:the, a
正确答案是: