生来就有的,对多种病原体都有防御作用,叫做 免疫,后天获得通常只对某种特定病原体或异物起作用,因此称为 免疫。
The old man never feels (alone/lonely)because he has many friends to talk with.
She tried to avoid (to meet/meeting)him because he always bored her.
He has made a lot of films,but (few/little)good ones.
﹣What's the (color/shape)of your present?
﹣It's round.
Stephen (is/come)from Ottawa,Canada.