名词的复数变化规律
主语单三人称时的动词变化
①在
中,当主语为
时,动词要用“s”型（即
形式）.
②所谓动词“s”型的构成,可按名词变复数的规则来记,即：
i）在动词尾直接加 s.如：
play—plays,want—wants,work—works,know—knows,help—helps,get—gets
ii）以字母s、x、ch或o结尾的动词加-es；如：
guess—guesses,fix—fixes,teach—teaches,brush—brushes,go—goes,do—does,watch—watches,catch—catches
iii）以
＋y结尾的动词,先变y为i,再加-es.如：
study—studies,carry—carries,fly—flies,worry—worries
③④强调如何将主语是
的
变为否定和疑问句.现举例说明（用划线部分来说明
）：
1）His mother works in a factory．
His mother doesn’t work in a factory．
Does his mother work in a factory?
2）Mr Li teaches us English．
Mr Li doesn’t teach us English．
Does Mr Li teach you English?
3）My brother studies maths well．
My brother doesn't study maths well．
Does your brother study maths well?