颊窝毒蛇的毒牙是长的空心管子.The fangs of pit vipers are long, hollow tubes.只有四分之一的蛇具有毒液和毒牙.Venom and fangs are found in only a quarter of all known snakes.在蛇的进化史上,毒牙的出现是新的进步.A more recent advance in the evolutionary story of snakes i...
...the educational problems of disadvantaged children...贫困儿童的教育问题I was disadvantaged by illness.我因病而处于不利地位.The centre aims to help disadvantaged areas of Europe, mainly by fostering new businesses.该中心旨在帮助欧洲的贫困地区，方法主要是通...
When his headaches developed Nick became bad-tempered and even violent.尼克出现头痛时脾气就变得很差，甚至还会动粗。Larry began suffering severe headaches and violent mood swings.拉里开始出现严重的头痛和剧烈的情绪波动。It is necessary initially to classify the he...