I, you, we, they のときは have を使います。he, she, it のときは has を使います。
I / you / we / they: have
I have a bike.
You have a nice room.
They have two children.
Not "They has two children." — say "They have two children.". Has は he, she, it のときだけで、they のときは have を使います。
やってみよう: Lars shows Mei a photo: My mother and father? They ___ a dog. (have / has / haves) 答え: have — 「has」を選んだ場合、その形は he/she/it のときだけです。they のときは have を使って They have a dog とします。
He / she / it: has
he, she, it のときは has を使います。
He has a bike.
She has brown eyes.
The cat has four legs.
Not "She have brown eyes." — say "She has brown eyes.". Has は he, she, it であることを表す形です。
やってみよう: Mei: Who is Matilda? / Lars: She's my friend. Matilda ___ a dog. (has / have / haves) 答え: has — Matilda ＝ she なので has を使います。
have それとも has？
選ぶ前に「だれ？」と考えてみましょう。he/she/it → has、I/you/we/they → have です。
He has a car. / They have a car.
She has time. / We have time.
Not "He have a car. / They has a car." — say "He has a car. / They have a car.". 同じ単語でも、だれが持っているかによって have か has かが決まります。
やってみよう: Hiroshi ___ a book. Amina and Mei ___ a book. (has … have / have … has / has … has) 答え: has … have — Hiroshi ＝ he → has。Amina and Mei ＝ they → have。
I've got = I have
話しことばでは I've got や she's got という言い方も耳にします。意味は I have、she has と同じです。
I've got a sister. = I have a sister.
She's got a dog. = She has a dog.
We've got two cats. = We have two cats.
やってみよう: Anna が I've got a brother. と言っています。どういう意味ですか？ (I have a brother. / I am a brother. / I want a brother.) 答え: I have a brother. — I've got は I have と同じ意味です。この 've は have の短い形なので、Anna は自分が何を持っているかを話しています。
やってみよう: Remember: who is it? Mei ___ three books. (has / have / haves) 答え: has — Mei ＝ she → has。（これがすべての基礎となる選択です: he/she/it → has。）