4. We would be grateful if you would introduce us to any companies _____ th is line of products. (A)engage in (B)specializing in (C)dealt in (D)interesting i n 。

6. Much as we would like to do business with you, _____. (A)we are unable to accept your order at the price you requested (B)we will be pleased to fulfill your order No. A116 (C)we are prepared to give a further reduction of 5% i n our quoted price (D)we expect to receive a new supply shortly 。