Sitting in her chair, she clasped her hands in order to conceal their trembling.
句意：她坐在椅子上，双手紧握，以掩饰自己的颤抖。conceal隐藏；隐瞒。pretend假装。uncover 揭露；发现。prevent预防；阻止。disguise隐瞒；掩饰。D选项与划线处意义最为接近，故选D。