电阻为10Ω的单匝矩形线圈绕垂直于匀强磁场的轴匀速转动，穿过线圈的磁通量随时间的变化规律为φ=5sin10t（Wb），线圈中产生的电流随时间的变化规律为（　　）

把铁粉和氧化铜的混合物加入到一定量的盐酸中，充分反应后过滤，在滤液中加入少量铁粉，无现象．下列判断正确的是（    ）

    Here are five kinds of animals. Elephants eat plants and fruit. They like water. The zebra ____in Africa. It eats leaves and grass. There ____only about 1,800 ____ in China. They eat bamboo and plants. The tiger is in Asia. It is large ____strong. It eats meat. It is good at swimming. Monkeys live in Africa, Asia and America. They eat meat, leaves, fruit and ____eggs.