many a boy and a girl 单数还是复数

用复数,这里有两个many a,相当于是复数.
“many a＋单数可数名词”形式上为单数,但意义上为复数(意为“许多”),若用作主语,其谓语通常与形式一致而不与意义一致(即谓语用单数).如：
Many a student has seen the film.许多学生看过这部电影.
Many a fine man has died in that battle.许多优秀的士兵死于那次战役.
Many a ship has been wrecked on those rocks.许多船只毁于那些礁石之上.
Many a young man has tried and failed.很多年轻人都试过,而且失败了.
Many a successful store has paid its rent cheerfully.许多成功的店铺都非常乐意地付了房租.
注：“many a＋单数名词”是一个非正式的结构,在口语或非正式文体中一般都用 many＋复数名词”代之.