下列各项中，会引起应收账款账面价值发生变化的有( )。 A．计提坏账准备 B．收回

    During the winter,     1    birds disappear. They fly away    2     the weather is cold. There are no insects in the air and they   3    find any food. These birds fly    4   warmer places. The weather is    5    and warm,
and they can find food easily.