She sits on the beach in the park.(改为一般过去时态)
∵sit的过去式为sat
所以,She sat on the beach in the park.(一般过去式无人称变化,所以无三单）
My brother didn't want the picture book.(改为肯定句)
因为, didn't =did not又因为是过去时态
所以,My brother wanted the picture book
My brother heard a lorry in the street.（否定句）
My brother didn't hear a lorry in the street.