three boys後面的動詞是複數。
boy 男孩,是個可數名詞。它的複數形式是boys。
Three boys are in the classroom.
三個男孩在教室裏。
Three boys go to school together everyday.
三個男孩天天一起上學。
The three boys are the best in the class.
這三個男孩的成績在班上是最好的。