How do I copy an element of composite type array into csv file?

Hi suppose I have composite type and table

create type A as(

    x float8,

    y float8

);

create table B(

    Ay A[]

);

insert into B

values(array[

    (1,2)::A,

    (3,4)::B]

);

Now I would like to export the first element of table B into an csv file:

COPY B(Ay[1])

The code above reported an syntax error.

How should I do it??

Thank you so much!

Shore