Scientists are convinced ________the positive effect of laughter________ physical and mental health

Many parents often warn their kids _____ candies or toys from a total stranger.— That’s right. They are afraid it bring some danger to the kids.

How do you learn English words —______ making flashcards.

She sat at her desk, with her eyes__________on the book, ________in its plot[ ]

下列各句中，没有语病的一句是（ ）