66. Since our profit is _____, we cannot gran t exceptions to our payment terms. (A)marginal (B)terminal (C)substantial (D)prudential 。

54. We appreciate your patience and please _____ that we will do everything i n our power to _____ that this type of error does not occur in the future. (A)assure....ensure (B)be assured....be ensured (C)assure.....be ensured (D)be a ssured....ensure 。