[判断题]砍剪山坡树木应做好防止树木向下弹跳接近线路的措施。
A.正确
B.错误

Over the years, biologists have suggested two main pathways by which sexual selection natural selection for characters that confer success in competition for a mate as distinguished from competition with other species; also: the choice of a mate based on a preference for certain characteristics may have shaped the evolution of male birdsong. In the first place, male competition and intrasexual selection produce relatively short, simple songs used mainly in territorial behavior. In the second place, female choice and intersexual selection produce longer, more complicated songs used mainly in mate attraction; like such visual ornamentation as the peacock’s tail, elaborate vocal characteristics increase the male’s chances of being chosen as a mate, and he thus enjoys more reproductive success than his less ostentatious rivals. The two pathways are not mutually exclusive, and we can expect to find examples that reflect their interaction. Teasing for microscopic examinatio
A. Female larks respond similarly both to short, simple songs and to longer, more complicated songs.
B. Male canaries use visual ornamentation as well as elaborate song repertoires for mate attraction.
C. Both male and female blackbirds develop elaborate visual and vocal characteristics.
D. Male jays use songs to compete among themselves and to attract females.