38. Small sailboats can easily turn over in the water ______ they are not managed carefully. (A). though (B). before (C). until (D). if

25.Ⅱ. Grammar and Vocabulary (D)irections: (B)eneath each of the following sentences there are four choices marked (A), (B), (C) and (D). (C)hoose the one answer that best completes the sentence. Leaves are found on all kinds of trees, but they differ greatly ________ size and shape. (A). on (B). form (C). by (D). in