题目

蛇等爬行动物在生殖上适于陆地生活的特点是，卵的表面有(     ) A.很硬的毛    B.坚硬的鳞片    C.柔软的壳    D.坚韧的卵壳 答案：D What ________ your brother ________ at five yesterday? [　　] A．were; doing B．was; doing C．did; do D．is; doing