Thorpe next set out to determine exactly when the chaffinch learns to sing.接着,索普就开始研究苍头燕雀是在什么时候学唱歌的.The chaffinch has three or four songs and produces them in a specific order.苍头燕雀合唱三、四种歌,唱的时候按着一定的先后次序....
Many school buildings are unsafe, and some are falling apart.许多校舍不安全，有些简直是摇摇欲坠。Dangerous undertows make swimming unsafe along most of the coastline.由于存在着危险的下层逆流，在大部分海岸线附近游泳都不安全。Critics claim the trucks are unsafe.批评家声称这些...
伦尼放缓车速，听到自行车轮胎在湿漉漉的路面上发出嘶嘶的响声。The tires of Lenny's bike hissed over the wet pavement as he slowed down.一阵嘶嘶的声音说明氧气正在放出.A steady hiss denoted that the oxygen was on.蒸汽漏出来时发出嘶嘶的声音.The steam escaped with a hissing soun...