Question

many a girl ___the movie.
has been / have been​

Answer 1

Have been is the correct option of your question

Answer 2

Many a girl have been the movie.

• Here by "Many a girl" means the plural form. So here obviously the word "Has" will not seat. Rather "Have" will sit.
• Not By "Have been"  means those many a girl was seeing the movie then .
• So the complete word will be - Many a girl have been in the movie.