Who often takes a walk in the playground?
A:Lisa.
B:Alice.
C:Mr Smith.
jié
wǎng
huì
wù
yè
____据
____然
教____
旁____
笑____
yǐ
cī
qù
niān
shì
____旎
吹毛求____
面面相____
____弓搭箭
____才放旷
天然森林很少发生松毛虫害,近几年来,某人工马尾松林常发生严重松毛虫害,其主要原因是