16.Mr Russel is a good teacher, but he often gives ____ lectures. A. excellent B. extensive C. sound D. tedioustedious 很郁闷的、很惹人烦的、单调乏味的excellent 优秀的、很好的out-standing 最优秀、杰出的extensive 广泛的、广大的sound n.声音、adj.非常好的、健全的