69. To defend themselves, oak trees use________. (A) chemical means (B) physical means (C) bitter chemicals (D) sandy materials

29.They _______ on the program for almost one week before I joined them, and now we________ it as no good results have come out so far. (A) had been working; are still working (B) had worked; were still working (C) have been working; have worked (D) have worked; are still working