皮筋绷在纸盒上,绷得紧,振动发出的声音____;绷得松,振动发出的声音____。
Linda with his father often _________ the zoo to see the animal.
为使“神舟”七号载人飞船安全着陆,应选择地形开阔、云量少、晴天多和人烟稀少的地点。下列地点最适合的是( )