题目

提出和创立细胞及细胞学说的科学家是（    ）A．施莱登、拉马克           B.施莱登、施旺 C．拉马克、达尔文           D.施旺、达尔文 答案：B －Dad, the type of computer looks cool．Can I have one? －No．You needn't buy a new one ________ your old computer doesn't work． [　　] A． if B． or C． unless D． since