⑴—When is Grandpa's birthday?{#blank#}1{#/blank#}

—It's on October 1st.                                                             A.

⑵—When is Grandma's birthday?{#blank#}2{#/blank#}

—It's on April 20th.                                                                 B.

⑶—When is mum's birthday?{#blank#}3{#/blank#}

—It's on February 24th.                                                           C.

⑷—When is your birthday?{#blank#}4{#/blank#}

—My birthday is on August 21st.                                            D.