talking birch bark 请问这是什么?

talking birch bark 请问这是什么? Stone Age people chewed birch bard tar,which forms when the bark is heated.后面为什么用现在时不明白,请指教! 英语翻译Cyclopropanecarboxylic acid2,5-Dimethyl-4Methoxy-3(2H)-Furanone5-methyl-2-hexanone3-Methoxy AcetophenoneAnisoleBetulline (Birch Bark) bark birch的 俚语 thriller bark thriller bark GMAT语法题,原题如下：From the bark of the paper birch tree the Menomini crafted a canoe about twenty feet long and two feet wide,with small ribs and rails of cedar,which could carry four persons or eight hundred pounds of baggage so light tha Bark up Dogs bark. bark 是什么意思 请知道的朋友帮忙说一下dogs bark这个句子我在一般现在时上面看到的s是不是应该放到bark上呀? Dogs___are usually quiet have started to bark.A.they B./ C.that请说明原因 Chinese Birch Solids & Veneer是什么材料 Be careful of the person who dose not talk and the that dose not bark''请翻译 THE BARK CAFE怎么样 bite bark区别 翻译：bark happily bark的意思