小学英语中“三单”的讲解主要涉及一般现在时态中第三人称单数主语后动词的变化规律。以下是详细讲解：
第三人称单数形式
be动词：is
一般动词：加-s，例如：play -> plays，walk -> walks
以s/sh/ch/x/o结尾的动词：加-es，例如：miss -> misses，wash -> washes，watch -> watches，go -> goes，do -> does
以辅音字母加y结尾的动词：变y为i，再加-es，例如：study -> studies，carry -> carries，fly -> flies
特殊变形：have -> has
习题精炼
The bird flies high in the sky.
She is in our school. She dances very well.
I find my cousin in the garden.
My father and mother go fishing on Sundays.
Lily likes climbing the mountains.
After school, he always has great fun with us.
Swimming is his favourite lesson.
Su Yang does not like my dog.
My little brother carries an umbrella every day.
The cat is Lucy's.
注意事项
有些动词的第三人称单数形式与原形相同，例如：he likes, she loves, it hates。
以s, x, ch, sh, o结尾的动词，要加上-es，例如：he watches, she fixes, it goes。
通过以上讲解和习题，可以帮助学生更好地掌握小学英语中第三人称单数的用法，从而在写作和口语中正确运用。建议学生在实际应用中多加练习，以巩固所学知识。