问题
                    
So suddenly ________that the animals in the zoo looked very frightened during the total solar eclipse (日全食).
                            A:did the sky turn dark
B:the sky did turn dark
C:turned the sky dark
D:was the sky turned dark
                        
                        B:the sky did turn dark
C:turned the sky dark
D:was the sky turned dark
正确答案是:
                        