— Is the baseball on the sofa?

— No, it's _________ the sofa.

下列物质需要载体协助才能通过生物膜的是    (    )

在一个变化剧烈的生态系统中, 生存机会最多的种群应是（   ）

Some advice(忠告)：

    ⑴ Always play in a safe place. A park is a safe place because there are no cars or trucks. But do not talk to anyone you do not know. Never go with a stranger into a motor car.

    ⑵ Before crossing the road， stop and look both ways. Look left， look right， look left again.

    ⑶ Keep away from houses or building that are being built or knocked down. Something might fall on your head， or you might cut yourself on broken grass.

    ⑷ Medicines or pills can be dangerous. Never swallow（吞下）any pills or medicines you find in the cupboard.

    ⑸ Wear a life jacket whenever you go out in a boat. Even if you are not in the open sea and the water is not deep， you should have your life jacket on. It's easy to fall out of a boat.

    ⑹ Do not put your head out of a car， bus or train. Many children have been killed by doing this.

长期患病的人，身体逐渐消瘦，其代谢情况是____作用大于____作用。