The blue tits(山雀) have been inspecting the nest-box again this year. The male is the house-hunter but the female will make the final choice. He lands at the hole and turns his head to expose his white cheeks as a signal to attract the female from where she has been feeding.
Among many birds that nest in holes, the male has a light-coloured patch on its plumage(鸟羽) which acts as signal for drawing the female’s attention to a suitable nesting-place. Unlike the blue tit, the redstart(红尾鸲) may be only the male that strikingly coloured and the female is not beautiful.
A few years ago I was lucky enough to spot a pair of redstarts in action in a Walsh wood. The male was leading an interested female to holes that he had previously(先前) checked out. He sat at the entrance of each hole and put his head on to show off his white forehead, or his head in to reveal(显露) his tail.
If the female failed to react to his visual signals, the male sometimes sang for extra effect, while gliding towards her on spread wings and tail. Once the female accepts by following the male through the hole the displays stop, you must be at the right place at the right time to watch them.
小题1:How do the blue tits choose their nest?
A．They choose their nest together.
B．The male chooses their nest.
C．The house-hunter chooses their nest.
D．The female chooses their nest.小题2:The writer was lucky to see ________.
A．how the male made his tricks
B．how an interested female played with the male happily
C．what the male displayed and won the female
D．that the male tried his best but failed to attract the female小题3:You can spot a pair of redstarts in a Walsh wood ________.
A．at any time
B．regularly
C．in April
D．occasionally小题4:The writer is probably ________.
A．a bird expert
B．a bird-hunter
C．a bird raiser
D．a scientist
，B错。各质点只在平衡位置振动，不随波前移，C错。x=6m处的质点此刻向下运动，再经过3s即四分之三周期，质点到达波峰位置，D对。