I saw the beautiful lady _____ this morning and this time she wore a white dress.[ ]

A. fluently

B. frequently

C. as usual

D. as if

蒸汽作为传热介质，既适合于体大的原料，又适合于体小的原料；既适合于动物性原料，又适合于植物性原料；既适合于菜肴，又适合于面食。如果对蒸汽加压，其温度变化范围也较大。